I think they're one and the same.

I know Hanover Township uses the Onspot on their ambulances. I'm also pretty sure the school buses have them.

There is at least one competitor, but the Onspot seems to be original and better quality. The chains on that other unit seem to look different in the holding position (although it works essentially the same way as the Onspot), whereas the ones I've noticed at rest - on ambulances, school buses, and oil tankers - seem to be the Onspot ones.