One specific idea, pre-approved for Y Combinator funding
paulgraham.com
paulgraham.com
Getting anything interesting onto an existing carrier's phones is a nightmare. Not only will you need to make a better phone OS, you will have to start your own MVNO. Helio has made an attempt - their "ocean" device might be worth looking at.
What will be interesting is whether they can be the operating system that a bunch of the Taiwanese ODMs use to become serious players in branded handsets (rather than just making them for other people).
[0] http://www.tat.se/conceptlab/
[1] http://www.youtube.com/profile?user=NokiaDesign
(Just realised I'm posting far too much in this story. Mobile UI is a great passion of mine. I think it's been downhill ever since the Nokia 3310. If any one else is passionate about improving the mobile user experience then please contact me at mobilaunch@danshub.com, I wish to pursue a startup in this area soon)
http://www.openwave.com/us/products/adaptive_mobility_suite/
Anyone else here love their Blackberry interace or hate it? Anyone here have an interface they like (and why)?
What would be better is a plug-in-able OS that would make the RAZR's menus tolerable (and maybe could be used on phones with even worse hardware).
Nokia S60's on the other hand are a dream to customise. I'm working on a new application launcher for my E61 right now and the difference is stagering. Being able to run python on your phone rather than java or C++ makes development tolerable. Hopefully nokias widgets coming this year will allow access to phone APIs from JS/CSS/HTML, then mobile will be as easy as web apps.
There's no date on the link, so it's not clear how recent it is.