Ask HN: Need an opinion on the iPhone app idea

The idea is to write a Web proxy app for the iPhone and configure the phone to channel all traffic through it (by configuring proxied network access in Settings). This is with the purpose of monitoring the traffic that goes to/from the phone and with the potential of blocking some of it (i.e. ads and invasive tracking). I am a programmer, but I am not familiar with AppStore guidelines/restrictions, nor do I know if all apps are required to go to the Internet through the proxy when one is configured at the system level. Can anyone comment on the feasibility of the idea from both angles?