I've been looking on ebay for a pair for my wife and I.  Only issue is she is 85 pounds soaking wet, and most are listed for arms 10 inches around min so they're gonna be too large for her.

I have a Tunebelt.  I tried putting it on the largest part of my forearm, which is 10" and got it pretty snug, but that was by extening the end of the band into the section of velcro that's supposed to hold down the headhphones wire.  At least that's what I use it for.  So it means that that flat that is either for the headphone wire, or maybe micro size adjust sits up.  It wouldn't be a big deal, and is nice and tight, but that's at 10".  I tried on a thinner section of my forearm (9") and it was a bit loose.  Maybe wrapping something around the arm at that point?  That would be my only suggestion.

(I can post some pics of my 10" configuration if that would help explain it).

I use this for my Droid, which is a tight fit and a touch long, but has worked for 1000km of running.

I'm heading out for the first time on Monday and was wondering how to secure my smartphone.  I remembered I had purchased a DryCase this summer.  I had gotten one for my Android phone and one for my Nook tablet.  The smartphone one comes with an armband.  I'll test it out.  It does have the benefit of being completely watertight plus still have the ability to plug in headphones and be able to use the touchscreen.  There's also more than enough room to stick an ID and key in there as well.  It may not have been made specifically for running, but it should get the job done.

Any new suggestions for Iphone 4 armbands?

I'm considering this one:

Marware SportShell Convertible Case for iPhone 4/4S

Try The CellBand. It is a terrycloth wrist band converted to hold Smart phones and small devices. They make two models $6.99 & $7.99 Free Shipping. You can also buy at wholesale $1.50-2-00 ea min 10. http://www.cellband.com