Hi, I should let you know that you can't record calls on all android phones, just on few. Most of them have this functionality disabled on hardware level and it can not be implemented in an application. However if a phone has this disabled in hardware the app can use the microphone to try and catch the conversation, it will be poor quality though. So I can make an app that will work with phones that have the hardware requirement and use the microphone for the rest. If you think that this is not an option then please do not choose me for your project. Let me know if you have any questions. Regards,
Ivan