We also have a desktop app which works very similarly in terms of setting up proxy and installing the certificates. The fundamentals with which we are building Requestly makes it different from other tools in this space. We intend Requestly to be used by team, easy re-use of the mocking configurations. The intent to go with SDK based approach is that it is one-time setup while using an external proxy will always require you to configure your phone every time which is painful. Like you said, local proxy servers can be flaky sometimes and you may eventually end up spending more time on the tool rather than your actual work.