I just saw this article on Fark.com and immediately thought of using it to track PWCs. Wasn't sure where to post since there is no PWC General forum.

Garmin GTU™ 10
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Looks like it's $199 and includes 1 year of service, then $49 a year after the first year.

Not trying to advertise or anything like that, but it sounds like another good alternative. I'm not sure if there is a way to rig up backup power to it. *shrugs*

I like how they advertise it for animals, not exactly sure how you'd attach it.