Android SMS App
<p>How difficult would it be to build an android app that responds to all SMS from a certain number.</p>

<p>Given a certain regexp on those SMS responds with an answer to a certain number.</p>

<p>Example input: "HelloWorld 12345"</p>

<p>Example regexp: "([0-9]{5})"</p>

<p>Example output confif: "Purchase $2"</p>

<p>Should give "Purchase 12345"</p>

<p>Is this possible to build on Android? Is there perhaps already an app for this?</p>
