I received mine recently as well. Paired easily with my 310XT, the Garmin detects it with no problem, and works as advertised.
I'm using this mainly to keep cadence constant while increasing speed as a simple means of measuring/developing power. A metronome could also be used, but measurement on the fly is more versatile.
I see that there is at least one (strain gauge) power meter for kayaking under development http://kayakpowermeter.com/products. Power meters revolutionized bicycle training and might do the same for kayaking, if they could be made portable and inexpensive.
Has anyone used one of the accelerometer devices (attached to the boat) that estimates (calculates) power?
YakCatcher Rod Holder
URCHIN Portable Anchor
Kayak & Canoe Covers
Touring Kayak Paddles