There’s a new kid on the wireless carrier block, and Republic Wireless aims to out-maneuver the bigger, older guys by delivering $19-per-month unlimited data plans.  The only catch is that you can’t bring your own device– you have to buy a phone from Republic– and right now there’s only one, low-end smartphone to choose from.

That low-end Android phone is Motorola’s DEFY XT.  While the DEFY might suffice for a new, casual smartphone user, it is definitely not for a power user.  The phone is powered by a now-relatively slow 1GHz processor and runs the now ancient Android Gingerbread (Android 2.3) — although it is upgradable to Android 4.0 (Ice Cream Sandwich) if you aren’t afraid of  rooting the phone.  The DEFY has a 5 megapixel camera, but only standard (non-HD) video capture.

On the plus side, the DEFY XT features Corning’s Gorilla Glass for resistance to scratches, and has rubber flaps covering its ports that make it dust- and water-resistant — a unique feature that might prove a strong selling point if you spend lots of time in dirty environments, by the pool, or…maybe if you’re a dolphin trainer.  The phone can fall from about three feet and be completely rinsed or submerged in water for up to thirty minutes without damage.

The DEFY uses Sprint’s 3G networks, so you won’t get 4G speeds, but Republic has set up the phone to automatically switch to Wi-Fi whenever it’s available.  This is Republic’s trick to keeping costs down, and the carrier promises un-throttled data service as long as you “play nice” and try to use Wi-Fi networks as much as you can.

You can pre-order the DEFY XT for $259, which includes the start-up fee and shipping and handling. Republic will charge the first $19 monthly membership when your phone ships, rather than waiting for you to activate it.  There’s a 30-day money back guarantee on the phone, but since Republic currently has no alternative devices, you’ll have to find a new carrier if you return the phone.  For more details, see republicwireless.com.