How to open the application from my android application with no launcher

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http://stackoverflow.com – I have 3 android applications. One main application call other 2 applications (main application will be interface for other 2 applications). I would like to have only one icon of this main app. I have 3 applications they can be downloaded separately. Now I need the other applications to check if the main application is installed. If not, download and install main app. But how can I do that, if the secondary applications haven't got LAUNCHER ? Is there any way to do install main app from app without launcher ? Main app has android manifest: <intent-filter> <action andr (HowTos)