Dumb-ish HRM question

[demandypants]

Hi there lovely ladies of H&F.  I am considering investing in an HRM strap.  but I am so confused. So I have a garmin 210 in the house I can use, but I am honestly looking for something to use in spin class and out on runs but I am totally happy with my droid phone apps (endomondo) for my outdoor runs. so here comes the dumb questions. Would a garmin (or other brand) HRM pair with the polar gym equipment? Would they link into endomondo if I went Pro?  Or do I need the intermediary device like the watches to make that work?  Any other things I should consider before I buy? 

[spunkypenguin]

The Garmin will not pair up with Polar gym equipment. I just wear my watch when I'm spinning or doing anything else indoors. I don't have any of those apps, so I'm not sure about that stuff. I will say that it's not that bad to wear a watch and an armband (I have my watch and ipod, so I can't imagine carrying the phone in an armband would be too different)