“App Update Notifier” is now available in the market. There are two versions. One is for Android 1.5 and 1.6 devices. You have to provide your username and password in the settings. The other one is for Android 2.0 and above. It makes use of the AccountManager, so u don’t have to provide any login information.
“App Update Notifier” notifies you about updates for your installed apps. It has a background service for update notification as well as a GUI to check manually.
Go check it out. Just search the market for “Goddchen” or “App Update Notifier”. Or have a look at the two appbrain links: