Sub7,
What you propose is very simple and effective. Basically what I do is hold the last update time in the application. At start up, but only once a day, I call a php script which checks for any more recent files on the server and passes a list of updates required. The app then downloads them using httputils.... For security the app passes an email address and 'AndroidID', which must match those held on the server, before it aloes the download - Not hi-tec or hugely secure, but good enough for my purposes!
hope this helps,
Douglad