Imho from using this device, a seperate app shouldn't be necessary to keep your memory at a good level. For me, all it takes is opening Settings -> Applications -> Manage applications -> and from here I click the menu button and press Filter. Then select Running and now you see all running apps. From there I just close off any app I know I don't need running (emulators, browser, Pandora, etc.)
way too much work, there should be a simple one click close, not with the froyo not allowing this it sucks.
