If paying $29.99 a month for unlimited wireless talk, text and data sounds like a good deal, listen up: Starting in about a month, you\u2019ll be able to do just that, no contract required. However, there are two caveats \u2014\u00a0and they are big ones.\nThe new service, announced this morning by Cablevision, is Wi-Fi only, meaning it will work anywhere you can get a Wi-Fi signal, but if you don't have Wi-Fi, you don't have service. The option is, for now, also limited to customers who own a Moto G Android phone. However, Cablevision will eventually expand the service via an app to other platforms, including iOS and Windows Phone, though the company has not yet said when that will happen.\nIf you're a Cablevision broadband customer, the service, called Freewheel, is even cheaper at $9.95 a month, and the cable giant will sell you a Moto G for $99.95.\nDrawbacks aside, this service represents an important breakthrough in the wireless world. It's the first wireless service of its kind that's based exclusively\u00a0on Wi-Fi, and it is much cheaper than conventional plans. The inability to use a cellular connection is obviously a limiting factor, but Wi-Fi signals and hotspots are getting easier to find in most urban areas. If you have a Wi-Fi router in your home or office, you'll be able to use the service anytime \u2014\u00a0a real advantage if you're in an area where cellular signals are weak.\nThe service makes good sense for city dwellers on tight budgets, it could be a good phone to give to a child, and it relieves you of worries that you'll blow through your data cap and get stuck with hefty overage charges. The service also works "anywhere in the world," according to Cablevision, so it could be well suited for frequent international travelers.\u00a0\nFreewheel is also important for another reason: It's a challenge to the leading wireless carriers' business models. I suspect that all, or at least one or two, of the U.S. Big Four carriers (AT&T, Sprint, T-Mobile and Verizon) will eventually offer some variation of a Wi-Fi based plan. We could even see Comcast join the party.\nT-Mobile already lets you make calls via Wi-Fi, but it doesn't offer a cheaper service plan for the option. Google is planning a service that lets you make wireless calls via Wi-Fi, but unlike Freewheel, it will fall over to cellular if Wi-Fi isn't available, according to the Wall Street Journal,\u00a0and will presumably be more expensive.\u00a0Discount carrier FreedomPop, which resells Sprint cellular service and requires a Sprint phone, also\u00a0has a $5-a-month Wi-Fi plan that's essentially a supplement to its standard offering.