As Sprint transitions between WiMAX and LTE for its 4G network this year, so far there's only been one device announced which can bridge the two: Sierra Wireless's Tri-Network Hotspot. It's safe to say that this little mobile hotspot will be invaluable for Sprint business subscribers in 2012.

Also known as the Sierra AirCard 803S, this thing looks like a table: it's resting on a gigantic battery, which speaks to the epic power requirements needed to support three modems (LTE, WiMax, and 3G EVDO.) It's kind of cute, actually.

The Tri-Network Hotspot has the same display as the existing Sierra Wireless Overdrive Pro ($49.99, 4 stars), delivering network, signal and battery information. But when it boots up, it searches for first LTE, than WiMax, then 3G. Because we're talking about three different modems here, each one gets turned off when the next one is turned on, and then each one is woken up occasionally to check for a faster signal than the hotspot has at the moment.

Okay, it's a kludge: while the soft-touch plastic hotspot is as elegant as something with a huge honking battery could be, it isn't nearly as slim as Verizon's upcoming Jetpack hotspot, nor as elegant as Sierra's existing Overdrive Pro. But I think people will be willing to take a slightly thicker hotspot in exchange for being to access the best of several available networks

Sprint's LTE network is coming by midyear, the carrier has said. The hotspot is coming with it.

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