Four old men gathered at the first tee, staring into my iPhone 3GS and asking rapid-fire questions about the Golfshot GPS app."There's no monthly fee?" one asked repeatedly."No monthly fee," I replied."I heard there are problems with the battery. Is that true?" another asked. "How accurate is it?""That's what I'm here to find out," I told them. "I also read that it takes a while to get a GPS reading, so I'm sorry if I take a little longer to hit my shot. Please don't hit into us."Can you get there in two?My playing partner, Ken, a Buddhist reverend somewhat adverse to technology, waited patiently for the chatting to subside before teeing off. Meanwhile, I called up the course on Golfshot\u2014there are more than 15,000 mapped courses\u2014 and put our names into the app's scorecard (which pulled Ken from my iPhone contacts list).Figuring execs need to get e-mail and phone calls on the course, I kept the iPhone's push notification on even though it might drain the battery. I checked the "disable auto-lock" in Golfshot's GPS settings, which the developer recommends to speed up GPS readings. I also took a mental note of my iPhone's current battery life, 96 percent.Then I teed off, wayward left.I'd decided to test Golfshot GPS for the iPhone at the Jack Clark golf course in Alameda, California, because the public course is fairly easy and cheap, which should appeal to the iPhone masses. That is, golfers preferring to pay $30 for Golfshot rather than hundreds for a standalone golf rangefinder would be happy to play there. It's also a tip of the newsboy golf cap to Jack Clark, the straight-shooting sports editor of the Alameda Times-Star for six decades.The other reason I chose Jack Clark is because I couldn't get a tee time at Harding Park, 30 miles west over bay water, where the President's Cup is taking place this week and where Michael Jordan illegally smoked a cigar yesterday during a practice round.Yes, smoking is banned at public golf courses in San Francisco but not in Alameda. With my briar pipe in one hand and the iPhone in the other, I faced my first dilemma. In order for the Golfshot GPS app or any GPS device to be really effective, as well as keep a pipe lit, you've got to carry both of them with you. They don't do any good sitting in the golf cart.Thus my convoluted shot routine went something like this: place the pipe near my ball (not using it as an aiming device, mind you), wait for a reading on Golfshot, put the iPhone in sleep mode, holster the iPhone and, 20 seconds later, flub my shot. Naturally, I blamed bad shots on the iPhone. Its added weight\u2014 4.8 ounces\u2014on my hip threw off my svelte swing, I figured, resulting in a triple bogie on the fifth hole. That's my story."I think the app is hurting your game," Ken said. "You're relying too much on technology, Tom. Golf is about feel."I bowed humbly even though my frustration level was rising in direct proportion to the drainage of the iPhone battery. Shouldn't your head be shaved, Zen Master? I thought. But he was right: Battery life had become part of my swing thought.The battery had dropped to 93 percent after the first hole. I quickly calculated that I would finish the round with a battery percentage in the low 40s. This would be above my goal of 20 percent battery life, the point where things start to go south on the iPhone. Hopefully, I wouldn't get a lot of telephone calls and e-mails. To save juice, I immediately put the iPhone to sleep after getting a yardage reading.But I was getting fed up with the time it took to get a yardage reading. Coming out of sleep mode, the iPhone took too long to "acquire" satellites. When yardage finally popped up on the screen, it kept changing. This kind of lag time and flaky information almost made Golfshot unusable."So do you want to know how far you are?" I asked Ken. He nodded thankfully and waited for me to give him the yardage. And waited. "You're 163 to the center," I said at last. Ken pulled a club and addressed the ball. "Wait! You're 166," I shouted."No, you're 158."The good reverend gave me a sideways look.Somewhere on the back nine, I knew my battery would survive the day. That's when I made a critical decision to put the iPhone in sleep mode only when I was putting on the green\u2014and this fixed the lag time. Now constantly connected to satellites, Golfshot showed yardage in real-time even as the cart moved toward the ball. The yardage didn't flutter as I stood next to the ball.Judging from yardage markers, I'm guessing Golfshot's yardage was accurate to within seven yards or so. If your game requires higher levels of accuracy, which probably means you spend a lot of time and cash on golf, then forking out $300 or $400 for a standalone rangefinder won't be a big deal to you.Highly accurate laser rangefinders like Bushnell Yardage Pro and battery-fueled GPS rangefinders like SkyCaddie and Garmin Approach cost more than two rounds at Harding Park ($155 green fee). But they're really fast at rendering yardage. Many rangefinders are waterproof for winter and springtime golf, whereas liquid is the death knell of the iPhone.For the rest of us, here's the lesson learned about Golfshot: Buy a battery pack so you don't have to worry about running out of juice while keeping the iPhone connected to satellites. (I ended the round with a battery percentage in the low 50s but have no idea what it would have been had I limited the number of times I put the iPhone in sleep mode for the front nine.)One thing pricy rangefinders don't have is cool software for scorecards, shot tracking and statistics. To this end, Golfshot's scorecard and analytics are very easy to navigate and use. It's the killer part of the app. By learning the number of your putts, Golfshot automatically keeps track of greens in regulation. Golfshot also let me easily record hit and missed fairways, sand shots, and penalty strokes.Golfshot even let me track the distance of my drives. This was a mixed blessing. After I hit what I considered a bomb, I'd track the distance. "How far?" Ken would ask. I used to think that I regularly hit 280 yard drives, but Golfshot brought me back to reality. "Not far," I'd say sheepishly.Another great Golfshot feature: With a push of a button, you can call up a Google map of the hole you're playing. By simply dragging your finger on the screen, you can find yardage to various points on the hole, as well as the yardage from those points to the green. Golfshot automatically showed layup spots for every hole based on how far you hit certain irons, although I didn't find this very useful because I rarely layup.Stats don't lie.The best part about the software comes after the round while sipping beers at the bar. There's no need to add up scores; it's all presented in a traditional scorecard format along with statistics that show quite clearly how you blew up. For the record, I missed 80 percent of fairways with 40 percent going left and 40 percent going right. This led to 17 percent greens hit in regulation and a dastardly score of 96. There's percentages of scrambling ability and sand saves, along with putting averages and scores by par. Suffice to say, I've got much work to do.Stats are sent to Golfshot for safe keeping and viewable by hitting the "statistics" button. These stats, shown in graphic charts, are updated with every round you play giving you an average for various areas of the game. For a one-time cost of $30, Golfshot is a steal. (Of course, a Mophie Juice Pack will run you another $80 but you can use that battery pack for more things than golf.)Golfshot stores all your separate scorecards on the iPhone, while a scorecard for your most recent round is automatically emailed to you\u2014as well as to anyone in your group that Golfshot pulled from your contacts list. The downside is that the app doesn't ask you first."I got the scorecard so now they have my email and know I play golf," Ken said, adding, "but I haven't gotten any golf advertisements ... yet."Full disclosure: Golfshot sent me a promo for the app to test out. What are your favorite iPhone apps at play? Send me an email at firstname.lastname@example.org. Or follow me on Twitter @kaneshige. Follow everything from CIO.com on Twitter @CIOonline.