It's called Search2Play, it lets you play and pause your music by pressing a button on your device. On most devices, it is the search key. Currently, the Nexus & MyTouch 3G both use the Search key, whereas the Droid uses the Camera key. If you have physical keys (i.e. Droid, MT3G, G1, etc) then it will work when the phone is locked, but if you have capacitive keys (Nexus, Moment, Eris, Incredible, etc) then the screen must be on (lockscreen works, and fully unlocked of course).
It is available on the market under the name "Search2Play (Root Required)". It's totally free.
It requires root permissions to install. It also requires that you have a version of BusyBox that supports the "cp" command. Only Droid users probably have to worry about the busybox version, as most other custom ROMs have that already. Droid users, I recommend CyanogenMod for Droid or Bugless Beast as I know both of them have the right version.
It does not run in the background or install a service, just makes some changes to a few files on the /system partition.
The UI is very simple, just two buttons and some text explaining the app. Once you hit install, it will ask for permission to use root, you must hit accept or the app won't serve its purpose
The other button, "Restore", lets you remove the mod and go back to stock settings, where the search button brings up search, etc.
Hero (GSM & CDMA)
Galaxy S devices (all US variants and probably the i9000 as well. It's not tested)
Droid 1 (I've been told DX & D2 work as well, though I'm not sure how :?)
Evo (must be NAND unlocked or S-OFF)
Desire (must be NAND unlocked or S-OFF)
Free Version on Market:
Or click this from your device: Search2Play Free
See the Market to view a screenshot. Please give me some feedback. Thanks! Hope you enjoy the app :
FOR DEVICE REQUESTS SEE POST #3