http://www.sunpass.com/
i'm not sure i'd get one if you're not going to be crossing the bridge on a regular basis, at least until the 331 bridge becomes a tollway.
these are currently where sunpass works:
* Turnpike Mainline
* Homestead Extension (Miami-Dade)
* Sawgrass Expressway (Broward)
* Alligator Alley (Broward/Collier)
* Seminole Expressway (Orlando)
* Southern Connector Extension (Orlando)
* Suncoast Parkway (Tampa)
* Veterans Expressway (Tampa)
* LeeRoy Selmon Crosstown Expressway (Tampa)
* Polk Parkway (Lakeland)
In Miami-Dade, SunPass works on the following MDX roads:
* SR 112 - Airport Expressway
* SR 836 - Dolphin Expressway
* SR 874 - Don Shula Expressway
* SR 924 - Gratigny Parkway
In the Orlando area SunPass works on E-Pass and O-Pass roads.
SunPass also works on the following bridges:
* Sunshine Skyway (St. Petersburg)
* Pinellas Bayway (St. Petersburg)
* Mid-Bay Bridge (Niceville)
* Garcon Point Bridge (Milton)
In the Fort Myers area SunPass works on all three LeeWay bridges:
* Midpoint Memorial Toll Bridge
* Cape Coral Toll Bridge
* Sanibel Causeway Toll Bridge