Add a new interface to a pre-existing open source android application - Paying more than $10

Hi, We are looking to add a new android interface for an open source secure messenging system. If you can modify existing android open source files and tweak them to what we require then you could be what we are looking for. Application is similar to some of the most popular secure messenging systems out there and will need to have implementations such as destruction of messages for an allocated time selected by the user as well as the ability to wipe the application remotely. We only need the front end and certain implementations added. So for example imagine you are modifying the implementation of Signal Secure Messenger, this is the kind of project this will be but only the front gui with our branding. Thanks