What I\'m trying to do is this:
not from an SMS I don't think - but you could look at push notifications which can be sent from your server. I haven't used them yet, but the way I understand it you can send a notification from your server and link it to the app.
http://developer.apple.com/library/ios/#documentation/NetworkingInternet/Conceptual/RemoteNotificationsPG/Introduction/Introduction.html
sorry, thats probably a better link
iOS does not implement a url scheme for launching browser based (ie. web apps) in standalone mode. ... But apple should though :) Apple implements parsing of urls to youtube.com and redirects them to the video app.
If they store the URL to the app placed on the home screen it would be a simple task to redirect links to that app.