spot messinger ?, those who own, in here

I've use the spot and found it generally OK.....

it is no replacement for an EPIRB or PLB, however. Ref your usage;

1. I'm pretty sure it has to have a clear view of the sky, but that should be possible.

2. The tracking only works for 24hrs so you will have to push the button again ever day.

3. They specify lithium batteries so I am not sure how sensitive to voltage fluctuation it is, if you wire it to the boats system.

4. How near to you boat are you? If you check the position daily what happens if the boat has dragged (critical, i.e. on the rocks, messy, i.e. into other boats etc.) ?

5. WAAS require accuracy of 7 meters or better both vertically and laterally, 95% of the time, as far as I know.

I would spend the $70 + the $150 per year on a bigger anchor, IMHO.

Scotty, the SPOT is designed as a one-shot device, essentially the batteries will last maybe one week and you've got to manually press the button at least once a day. In order to do what you want to do, you'll have to go out to the boat every day, rain and shine especially rain, and change the batteries at least once a week. And IIRC it prefers Lithium AA's, which may be something like $10 for a four-pack. Or, you can hack into it, totally voiding the warrranty, to apply an external power source and a daily trigger to push the "track" button. Easy enough to do--if you're into electronics.

OTOH devices likethe zoombak already are built for vehicle use and constant use and the geofencing is including in their firmware load. (Geofencing being the standard term for "anchor watch" and similar.)

100 yards is tighter than you think. You've got a normal swing on your anchor or mooring, that might exceed fifty feet. Then there's a normal fluctuation in GPS, even with WAAS GPS, which I don't know if either unit uses. If you want to pin the locaiton down tighter than 100 yards, expect false alarms. Or, a SEAL team laser-targeting a Predator drone on it.