Is there any simple way to protect the Android App and update it?
<p>I developed an Android App and installed to three users' cellphones through Eclipse and USB connection. I don't want to put the App to google market. Now I got two problems:</p>

<ol>
<li><p>How to protect the App and make it invalid in other cellphones. I know we cannot protect it 100%, I just don't want the App to be easily copied and run on other devices. What I have done was hard coding in my program to compare the AndroidID (save the AndroidID to a string and compare with current AndroidID). The problem is that if I have 100 users, I have to hard code 100 times.</p></li>
<li><p>How can I keep the users updated. Do I just upload the updated App to my own server and give them the link to download and install? In this case, the first problem comes out again: how to protect the App?  </p></li>
</ol>
