[iDonev]

I'm searching for a tweak that puts a status bar icon whenever there are background apps running on the device. Any suggestions?

Edit: I'm also looking for a tweak that hides the cellular bars (but not the connection type, i.e. 3G, EDGE, WiFi) from the status bar.

[brutal truth]

Backgrounder gives you complete control over native backgrounding. It can specify exactly which apps you want to use in the background. It also puts a status bar icon when that app is being backgrounded natively or a badge on the icon if you like.

CleanStatus gives control over the status bar. I'm not sure what firmware you are on and if it's compatible but give it a shot. It's the best one I found. I just hide the carrier name with sbsettings though.