I have a Cardiosport HRM which has a hard strap (to about the outside edge of each boob, then soft elastic round sides and back) and don't get chaffing at all from it. The times I do chaff as when when wearing certain poorly fitting spoorts bras or sometimes doing long swim sessions. I've not tried this as have not had a prob with my HRM but man=ybe those with chaffing issue could try using a bit of vasaline on the trouble spots (but obviously not on the sensors) I find this really helps stop my swimmers chaffing in salt water.

Colby - have you tried rubbinng a bit of spit on the HRM sensors, I find this is usually enough to get a good connection and readings before working up a sweat.

BTW I have also had a fair bit of success using my HRM in the pool (though not in salt water). I just twist the strap around my swimmers at the back to help hold it in place. I think women have more luck with HRMs in the pool as we swim with our chests covered which allows the HRM to operate properly.

Back to the OP, the 2 hand instantaneous nature of strapless HRMs was what put me off one when I bought mine. Could you borrow one for a while to see if you can get used to putting it on before each session before you invest in something you think it unlikely you will use?