Android Market update notification not working properly for you? No problem! App Update Notifier is the solution.
App Update Notifier not only checks apps that you installed through the Android Market, but ALL your installed apps, even those from third party markets...
Also features an optional background service which notifies you automatically if new updates for your installed apps become available.
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Please note that App Update Notifier will (of course!) send a list of your installed apps to the server to check for the online version infos!