Currently I'm trying to integrate Sinch with Appcelerator Android, to make my life lot easier, is it possible to answer or hangup just by calling a REST API ?
Appcelerator or another JavaScript based sdk is not supported by Sinch. It may work with our JSSDK but there is no Rest api calls to accomplish this. There is a lot of processing going on the client side in voice calls so you will need a native SDK or you can try JSSDK but we do not officially support it