If it's not too late..
I can highly recommend the Klipsch s4i.
Not only were they pretty light (and completely unobstrusive when running - the remote wasn't heavy at all) - taking calls/volume adjustment/song selection on the run was very very handy.
Then again, if you don't want to be disturbed, just put your phone in airplane mode
(or leave it at home!
)
Worked fine with my little iPod nano - though I could really hear the difference in sound quality when listening to the same song on my (then) iPhone 4 vs. the iPod nano - though I wouldn't count that as a flaw of the IEMs themselves.
Sound isolation was fantastic - kinda made running a bit of a thrill, since you had to pay EXTRA attention to your surroundings so you didn't get hit by a car
I didn't dare cycle with these on!!
They're very very comfortable - I have very troublesome ear canals that were difficult to fit, so that's another thing going for it.
Sweat etc didn't matter - they stayed very comfortably secured in, with none of the itchiness/irritation from certain IEMs/tips when they've been inserted in for a while.
The only downside for these IEMs were their 'flimsy' cable, which wasn't THAT flimsy but definitely felt like a decent tug wouldn't do it any favours... the release of the new S4II (same headphone, just different tangle-free and durable cabling) ought to have resolved that problem.
Some people have complained the new 'rugged' version of these have a heavy remote. So I'd probably stick to version 2.0, being the
Image s4i(II).
Seriously considering getting another pair of s4i's for runs etc, since I lost my first pair of s4i's!! Apparently the sound is unchanged, it's just the cabling that's been upgraded.
In short: comfy, sound amazing, solid build quality (cabling issues fixed), LIGHT, unobtrusive to wear, and look great.
Hope this helps!