I used to have an antigravity jumpstarter then I lost it during a Sheetiron 300 What I didn't like about it is I would accidentally turn the flashlight on because the button isn't protected and it would drain the battery and you have a jumpstarter with no juice.
So instead of buying another one I instead used a Hobbyking 3S Lipo battery and made a harness for it with an EC3 (used to be EC5) connector. Cost me $15 and at 80% charge which is the storing voltage for LIPO batteries it will start my DR650 up No flashlight to drain the battery too It nice to have when you've been charging stuff off your bike overnight and drain it too much or if its really cold out. I made an adapter for it so it had some aligator clips so you can jump cars easily with it. I was able to jump a Toyota Previa and a Mitsubishi Eclipse with it with totally dead batteries.