Do you want to communicate with someone who is not able to pick up the phone..
If the app is enabled it looks at a incoming phone number and compares it to a pre-set number(s). If these numbers are the same the phone will automatically answer the call. You can also enable and disable speakerphone.
This app is activated by System intents. So you can leave the app and let it run in the background. But because of the use of the System intents it does not take up any battery and it is only activated by the system when a incoming call is detected.
Leave a phone with this app on a location you want to eavesdrop and call it with an other phone (does not have to be android). Your android phone with this app will atomically answer your call and you can listen to what is happening on the eavesdrop location.
Leave a phone with this app on a location with a person who is not able to pick up the phone (children, elderly, disabled) call and communicate with this person.
use your imagination...