Hey Ghost, I recently purchased a Scosche soundKASE from Amazon was a little worried at first it may not fit as at the time there was only one user review stating they also owned a Droid 4.
Been running with it for about 3 weeks now and haven't had a single issue, armband stays tight, I can still hear the speaker nice a loud, able to navigate the screen just fine.
The fit was a bit snug at first but now the case has stretched comfortably to where I can slide the phone in and out with ease, but it does not bounce or otherwise feel as though it will fall out on it's own.
The obvious limitations are sometimes the sound can be a little muffled depending on the placement on the arm, volume rocker buttons are mostly inaccessible but if you push on the sides of the case you can usually get it to register.
It does fog up a bit every now and then, but it has never affected my phone in any way.
Very happy with this purchase, works well with the Droid 4.
I cant post links yet so just search Amazon for "Scosche soundKASE - Android" it should be around $18.00 with like 4 reviews.