Which model(s) will do a custom heart rate alarm?

I am looking for the cheapest Polar device (chest strap I think as needs to be accurate) which will do the following:

a) sound an alarm (ideally in earphones) whenever my heart rate goes above a customizable level

and b) then either keeps sounding until it drops below again or plays a different sound when it goes below. I need this to repeat and infinitum as I work out.

Thanks!