Ice Cream Sandwich 4.0.3 is the latest version of Android that all android smartphones owners are waiting to update their phones to it. Meanwhile, Nokia N9 already got it thanks to "Project Mayhem".

Its not fully complete yet or you can say its an alpha version that only covers the basics of ICS, Screen, rotations sensors, Bluetooth, Wifi, phone. It also has software buttons (on-screen buttons) like the galaxy Nexus. The few hardware buttons that the Nokia N9 has are working too along with the headset buttons.

Project Mayhem Features:

- dualboot kernel (without reflashing), ability to choose OS after power on.
- 3D drivers, OpenGL
- hwrotation (portrait mode only, accelerometer HAL doesn't work)
- touchscreen (multitouch)
- hw buttons (volume, power)
- ECI accessory (headset buttons)
- USB networking
- lcd off in sleep mode
- alarm driver, RTC
- mounting MyDocs as "SDCard" [realized; NOT FIXED, but HACK EXISTS]
- basic video decoding (sw) and playback, youtube (choppy)
- basic CellMo functionality: network registration, USSD, SMS, data (GPRS/EDGE/3G), signaling. Actually, ofono/ofono-ril stack is used: all things that it able to do on the n900.
- bluetooth (scanning, can pair devices. I didn't test deeper).
- charging (note: without any notification in UI)
- sensors: accelerometer
- audio: playback (audio routing to: loudspeaker, headset or earpiece)
- lights HAL (lcd brightness)
- root access (via adb shell; su/Superuser.apk)

More Info and Instructions Here