What would the pitfalls be of blocking calls on Android by setting the ringer volume to mute, then having an app play the ringer?
<p>It's well-known on Android discussion forums and SO that Android's API doesn't have a good way of blocking calls. You can have an event trigger when a call comes in, but by the time your app suppresses the call, it has already rang once or twice.</p>

<p>My idea is to have an app that sets your ringtone volume to mute, then when a call arrives, it would look up the appropriate ringtone for that call and play it if the caller is in your address book. Effectively, it would block unwanted rings, though not unwanted calls.</p>

<p>Being a relatively inexperienced Android developer, I'd like to know what problems this might cause. What would be the major pitfalls, possible causes of bugs, and problems with the user experience (besides seeing their phone on mute, when it really isn't)?</p>

<p>Also, any recommendations on how to best implement this idea?</p>
