We might finally be on the verge of better and cheaper wireless services through Wi-Fi, VoIP, and SIP.

There were two announcements this week regarding the combination of Wi-Fi and cellular--one from AT&T and one from virtually unknown Republic Wireless, a division of Bandwidth.com. As is typical in the mobile space, the big story is from the small player.

Republic Wireless is a mobile virtual network operator (MVNO), which means they do not operate a cellular network of their own but rather resell services they buy for another operator, in this case, Sprint. First spotted by Jason Kinkaid at TechCrunch, Republic will be offering unlimited mobile voice, text and data service for a flat $19 per month with no contract--yeah, less than 20-bucks a month. The obvious question is "How can they do that and stay in business?"

Well, the answer is that Republic will be using a combination of Sprint’s CDMA cellular network and Wi-Fi, which they call "Hybrid Calling". Whenever the device is in Wi-Fi range (which they claim is 60% of the time), the phone will automatically jump on the cheaper option. The user does have to ensure the device connects automatically to Wi-Fi networks visited regularly, but there are several Android apps that can automate that.

We've had the ability to place VoIP calls over Wi-Fi for some time, but Republic seems to have come up with a way of doing it better. The traditional approach is to make sure you're on a Wi-Fi network, launch an app, and place a call; typically there's no inbound service. Republic has integrated this capability, and you can simply look at your phone and see if it’s on Wi-Fi or cellular.

There are limits to the deal, as you might imagine. The big one is the Cellular Usage Index (CUI), which is Republic's measure of how much costly cellular time you’re burning up; it is calculated using your last seven days of activity. If you're nearing your limit, you get a warning, and if you don't get your usage in line, they can bump you off the service. How much is too much? The Web site advises "you could consume 550 minutes, send 150 texts, and download 300 megabytes of data without crossing the community’s fair use threshold." The other gotcha is that there is apparently no Wi-Fi to cellular handoff like you find in T-Mobile's dual mode unlicensed mobile access (UMA) service; T-Mobile calls this service Unlimited HotSpot Calling. Wi-Fi to cellular handoff in an arrangement like this is pretty tough because they would have to set up a cellular connection to move the call, and cell call set-up can take 10 to 15 seconds.

Also, there is not much choice in the way of handsets--they have one, the Android 2.3-based LG Optimus; they do plan additional handsets in the future. As there is no contract, you have to buy the handset outright for $199, but they have a promo running through November 27 where they’ll discount the handset to $99 (use the promo code "welcome19").

Finally, if you travel internationally you can only make Wi-Fi calls, as the handset is CDMA rather than GSM. However, users have been pining for a cheaper option to "Big Cell", and on paper at least, this one appears to be one of the slickest. It remains to be seen if anyone other than the truly tight-fisted will find the Republic solution appealing, but the company seems to have come up with the best possible solution, given the limitations placed on them.

Expect to hear a lot more about this outfit in the coming weeks.