Priority Start?

http://www.prioritystart.com/
Anyone have any experience with these? It hooks into your battery, and cuts it off when there's just enough power left to start it up again. I do a fair amount of tailgating with the stereo going but the engine off, so I'm thinking this might work well to save the battery rather than randomly guessing when to turn the truck on every once in a while.

 

Looks to be a promising product.

 

Bumping an old thread, but I used to install them often. I worked for a shop that builds wheelchair accessable vans. Oftentimes, those vans are driven only to take someone to the doctor every week or two. Combine that low usage with added electronics, and sometimes car alarms, and the battery would die within two weeks or so. The Priority Start worked as advertised, never had a problem with one in our application.