http://www.mioglobal.com/Mio-LINK-Heart ... tID=1&RD=1
It's a HRM strap that you wear on your wrist. It "talks" to other devices via ANT+ or Bluetooth, so you can pair it with a Garmin and/or use it with various smartphone apps. It uses optical technology to measure your heart rate, so it does NOT depend on receiving your pulse as an electrical signal in the same way that regular chest straps do. I tried it out at the expo and it worked really well as I was just standing there. I hope it works as well while I'm running-- I'm told it should as long as the fit is snug, which it is. I'm very excited about it, because the Garmin HRM strap was driving me nuts (funny fit, erratic readings) and I was often not wearing it.
I'll update later after I've used it a few times.
Mio also sells a HRM watch (the Alpha) which uses the same type of HR receiver in a sports watch, but it doesn't have GPS or any distance measuring functionality.
It works pretty well. It does seem to cut out sometimes when my HR isn't that strong-- I'm not sure how to fix this. But overall I like it better than the chest strap.