Heart rate watch thingy

Since I have several friends who are in weight reduction programs etc. I thought I'd better mention today's offer from SVP - a heart rate monitor watch with a strap on sensor. I have no idea how good this is, but they claim to be offering about £50 off the normal price, £24.99+P&P instead of £79.99

http://24gone.com/?ref=hotbox

Offer ends at midnight Saturday.