I have built an android tablet application which is installed only from my web site - manual install.
I will need to be able to provide updates to existing users through the same site - without obliging users to uninstall the existing application.
What do I need to change in my (eclipse) project to permit this ?
Simon -
Apps are designed to be upgraded in place on Android. All you need to do is ensure that the version number of the app being installed is greater than the previous version.
You can still provide debug releases, simply increment a portion of the version to reflect that change and your users can keep getting updates. Otherwise, you may want to have an explicitly Debug and Release version that can be installed side by side and not conflict with each other, but that may be more trouble and confusing than its worth.