I've recently joined a gym and I'm looking for something to wear that will track my distance when using a fitness bike. I've googled it and looked at various sources but can't find a definitive answer. I'd like to wear it most of the time as I do a bit of walking with my job. A heart rate sensor is a must. And that's it really along with the distance tracker. I've got an iPhone too which tracks distance but not very accurately. If I cycle 8 miles on a fitness bike with my phone in my pocket it might read that I've done 4 miles which makes me wonder if it's accurate at recording my distance covered when walking. Any help would be appreciated thanks