I tried one of these briefly. Terrible device. For a start it is huge, ridiculously large, and with a bracket design that works only if you can have the computer directly in front of your stem.
Battery life is poor - and it takes two at a time. The heart monitor sender is a terrible design, 2 or 3 times larger than any other HR sender and not practical to wear. Most parts of the display are too small to read when riding at any speed. Avoid.