This is definitely something I have been waiting for! A stylus for your tablet which is pressure sensitive! For me this means I can stop trying to save for a Wacom Cintiq, which is probably the better product but completely out of my budget at this point in time.
It works by sending high frequency sound which is detected by the tablets microphone. So it will work in airplane mode.
High level of pressure sensitivity.
It also has two buttons which you will be able to customise to allow for varies functions.
I first read about this on kickstarter, link below, unfortunately the kickstarter is over.
However, you can preorder one from the website below. The only one taking orders as far as I can tell. The JaJa should be shipping at the end of July.