I have used one free android app name Last Message. This is a free android app available on Google Play Store. This application is very useful in the situation when our phone battery has been depleted in the mide of our important conversation. Last Message automatically send waring message to our friends and family that we are not in contact once the mobile battery has been gone. It runs in the background of our phone and does not effect other functionalites of our phone. You can also try this app Last Message
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