I'm currently developing a small Android app that will not be on the Play Store. It is a private business application that will be used for a non-emergency transport company. The Android app will show drivers a list of pickups and drop-offs that they will have throughout the day and allow them to update the status of those trips. What I'd like to do is have some method of updating the app during off hours or when the device is idle. Ideally, it would be great if someone has already written some kind of Android updater that can run as a service. However, I certainly wouldn't mind writing this on my own.
Either way, all it needs to do is pull an APK from our servers and install that APK. I usually don't like doing things sneaky like this, but our clients want it to be this way so that they won't have to go to each device and press OK on permission prompts and they don't want to leave the responsibility of updating the software to the drivers.
I understand the security concerns, but it seems to me that there should be some way to allow an app to auto-update itself if the user permits it. Also, our app is signed and includes a certificate on the device to verify that the downloaded app is legit.