Well,
Not sure what you want the bike computer for completely, but it does not appear you are looking for thing such as GPS etc ...but more a HRM with some basic cycling information as well.

My solution: Save some money, get a TIMEX Ironman HRM and a Cateye Astrale 8. You get speed, cadence etc... and then also have a HRM that can easily be used on and off the bike for whatever activity you want.