In reply to mitchellbowen1990:
Try five spring toggles with stainless steel springs on your compass cord (move up one-by-one to count 500m, back for the next 500m, and both robust and intuitive).
Re. fingers/in your head etc... never worked for me if distracted (I'd know the paces, but forget the 100) + it's hard to count to 10 with only nine fingers!