[Luke Hutchison] has come up with a rather clever hack to get multitouch support on the G1.
He wrote a patch against the Synaptics touchscreen driver. When two
fingers are placed, the driver reports the x/y of the midpoint and a
radius for the size field. If only one finger is used, the size is
reported as zero. The nice thing about this approach is that it’s
backwards compatible; the extra data will be ignored by current apps.
Unfortunately, Google’s Android team says that if multitouch is ever
added, it would identify individual fingers and definitely not using
this method.

[via ABN]