Thanks for your question!
The Polar H10 heart rate sensor is compatible with smartwatches, exercise devices, and phones that use either Bluetooth technology, or ANT+ technology to sync data. Without knowing which devices you're considering specifically, my recommendation would be to look at the specs of that device on REI.com, or the manufacturers' respective websites to see if the watch features Bluetooth and/or ANT+. Nearly all of the GPS watches we sell at REI have one or both of those technologies.
If you're accustomed to carrying your phone, and are looking for another workaround for carrying your watch on your neck, you might consider using the strap with the Polar Beat app which sends data right to your phone. We carry a variety of small running packs and armbands that would allow you to quickly access a phone, even in cold temperatures while wearing gloves.
If you're considering a new smartwatch, we carry many options and would be happy to talk to you in more detail about them. Specifically, it's best to know what features (aside from HRM strap compatibility) you need in order for us to help you make an informed choice.
I hope this clears things up a bit. Let us know if you have more questions!