In responce to Ewans original post, it seams that Noel Poncelet of Hassocks Hog has found a component that does everything that Ewan was asking for:http://www.hassockshog.co.uk/build_diary_2.htmhttp://www.hassockshog.co.uk/build_diary_2.htm
go to the entry on may 28th.
It talks about a fully auto-protected power MOSFET (VNP49N04).
This sounds really interesting to me if it works. Ive been thinking for a while now of designing a bolt on current limiter that modifies the signal going to an ESC or somehow switches the output off when the current reaches a preset level, but it seems a much simpler solution to just stick this mosfet in series with the ESC outputs.
would this work though?
Problems I can see:
1) dissipating the heat it produces
2) it would waste some power
3) its another component that could fail
assuming these problems could be overcome would this work to protect motors from over heating or help batteries last a bit longer?

Mark