Hobie - when I read the words my son removes his pump before starting to play Rugby, but has had the cannula ripped out by another player during physical contact, how can we prevent this? I quite clearly interpret this as a different problem to yourself.
All pumps as far as I'm aware have a similar 'bung cap' - the Roche one for instance is about 2mm if that thick and lies flat on top of the sticky pad affixed to my skin when in place and to rip the cannula out from above my pants and trousers, skirt or shorts, you'd need long and very strong fingernails to get enough grip on the hard plastic bit and rip it out - UNLESS the sticky pad itself was already loose and flapping about somewhere around the edges of it. However of course with the pump and tubing in situ then it's relatively easy to rip one straight off and out accidentally, if you're eg running past eg a door handle, tree branch etc, with the tubing on show and loose enough to catch on the handle when passing and rip the lot off and out - it ruddy HURTS and I wouldn't know that unless I'd already done it once either, would I?