Assuming it fits your GPS model, I think it would work just fine. As far as getting it to connected to switch off with the ignition, there are two options:
* Wire it to an existing switched lead, such as your headlight, taillight, etc.
* Wire it to an aftermarket relay.
I would recommend the later but the first is easier (and cheaper). The website doesn't give the current it draws, but it probably isn't that much (<1Amp I would guess) so it's probably reasonably safe to just wire it up with your headlight or DRL.
The better way would be to get a switched fuse block like the FZ-1
(or AP-2). There are other fuse blocks out there, too. You can also just run to an auto parts store and buy a 30Amp DC relay and an inline fuse holder.
A good soldering iron, some heat shrink, additional wire, a few connectors here and there, and wire strippers/cutters will come in handy, too.