As long as it draws under 5 amps (probably less than 3 as the fuse should be about 2X the draw)you should be good to hook it into the ign circuit. You just don't want to hook anything that draws a lot of current. The ign. sw. wasn't really designed to handle big loads and the contacts will eventually burn up with a high draw. That is when you go to a switching relay.

1997 T-100 4X4 Xcab,Warn Hubs
02 Camry LE
2008 Yaris