The new Android OS (currently only on the HTC G1) has a very clever login security screen which eschews the traditional alphanumeric password for a gesture based one. The screen has a three-by-three square of dots which you join together in any pattern you want with a single gesture. Considering on the iPhone you already open the screen with a side-swipe this introduces a level of security without increasing the hassle.

However, there appears to be one possible flaw. The oil on your fingers can leave patterns on the screen which means that gesture you use to unlock may be left visible in the trail from your crisp greased finger. The flip argument is that regular gesture movement while operating the handset would smudge that trail often enough to make it invisible.

As they say the best laid plans of mice and men are often undone by greasy digits. On a side-note this real-world hack has been commonly known for years to give away passkeys on those standard metal door locks (just look for which metal buttons are worn or greasier than the rest).

Pic and tip from Techcrunch