You can now build your own installable web apps for iPhone, iPad, and Android at: https://mobimorphic.com/ (update: the web apps will also work in the Kindle Fire browser, but as yet I haven’t found a way to install them to the home screen).
Note that you DON’T need to be a programmer to build one of these — that was the design goal. If you can use Google Reader or set up a Google Calendar or Flickr album you can use this. Conversely, if you are a programmer you can use the External Code block and go as far as your imagination and skills can take you.
I’ve been working on this stuff for about a month, and I think it’s time to let other people start beating on it. It definitely needs more extensive testing on Android — works fine on my cheapie Android phone and on my Kindle Fire, but there are about a billion different configurations of Android out there. Let me know if something breaks. Note that there are two links on that page — the first goes to a sample app that needs to run on a mobile device to be fully functional. The second is to the self-service app builder, which needs to run on a desktop or notebook using Google Chrome or Safari (no Firefox or IE support, sorry).
Supported resource types at present: Web feed (RSS and Atom), Twitter feed, Flickr photo sets, podcasts (both audio and video), YouTube channels, Google Maps, user-entered HTML (includes a WYSIWYG editor), external code, external site, phone dialer, SMS text message, iTunes store, email, Google Calendar, and Facebook.
Next steps: performance optimization, more themes, and better docs. I also have some ideas for cool new blocks, and want to make Facebook an internal resource (like Twitter) rather than an external link.