BGT-31: Genie BGT-31 Waterproof Sport Bluetooth GPS Data Logger with SD Expansion Slot
I got this for cycling and kayaking, and love it.   I've been pleasantly surprised how easy it has been to use multiple functions; the interface is surprisingly mature for such a gadget.     It easily and automatically logs tracks in internal memory and/or SD card at rates up to 1/sec, or after you've traveled a given distance. You can download tracks in google earth format and show grandma where you kayaked, then forgot to turn it off and drove home, and then had your son strap it on his bike for a ride: [