I see a lot of SO questions and answers relating to auto update that amount to the correct answer being "it can't be done without the user's participation". However, many of my apps have the "update automatically" checkbox checked in the Play store and I see them auto-updating and then notifying me in the notification bar that they have, in fact, updated.
So clearly it *can be done... I'd like to know what my various options are for getting my app to have this feature. Does it need to be in the google Play store? Can it be in some alternate store instead? Is it available to apks that are side loaded... etc.
TIA.
On standard phones, the only way it can be done is through the google play store, and only after the user opts in to automatic updates. It will stop working when the application's permissions are changed. Additionally, google can remove apps at will from your device.
The above applies to all Android devices which have google services and the play store installed. Additionally, apps purchased through the Amazon Appstore for Android are automatically updated on Amazon Kindle Fire devices, and some manufacturers have their own app stores which may include that functionality; Samsung and Lenovo come to mind.
If you control the hardware or have a rooted device, you can create/install a system app which can install any app without user intervention.