No more **** passwords?
A nice solution built by MERL to prevent shoulder surfing is to display a flickering picture and provide glasses that would be able to filter out these flickers resulting in a dual image:
This means that the display that can only be viewed with magic glasses.
Although the solution is simple, you can use this to “encrypt/hide” data quite well – i.e. show someone one picture while the person with the special glasses sees another one.
The only draw back is that the glasses need to be wired to the screen, making the solution not very portable.
This would also give a whole new meaning to “I can’t work today as forgot my glasses at home”