Jumper packs that can also inflate a tire are much smaller than a pancake air compressor, and they are just the right size to throw in the van or truck. These work great at a trackday, race, or even in the parking lot when the unexpected flat tire happens. Let to much air out of the tire at the track? No problem, this little compressor will put a few more PSI back in the tire in no time.
I have seen my fair share of bikes with dead batteries at the track as well. Someone leaves a key on overnight, or they forget to check it before they leave home. I can be very forgetful at times. The dead battery in the bike when I get to the track scenario runs through my head constantly (even though its never happened to me). I wanted to make sure I had a backup plan just in case it did happen. I now have the piece of mind that my jumper pack (security blanket) will help me get through the dead battery situation if and when it does occur.