Most cell makers let you secure your phone using a four-digit PIN number. That will keep your address book and other data safe and will keep others from running up minutes on your service plan if the phone is lost. But what if someone shoulder surfs you while you’re making a call and then steals your phone?

Start-up security company PINoptic has an answer: Picture-based PINs.

The PINoptic system adds picture icons to each number key on your cell phone keypad. When you want to unlock your cell phone, you punch in a sequence of pictures, not numbers.

What’s the difference between hitting numbers and punching pictures, you ask?

The PINoptic system will use ‘smart button’ technology to randomly redistribute the picture icons over the available number keys each time you want to unlock your phone.

PINoptic is currently looking for partners to license and develop its technology. No word, yet, on when PINoptic security protection may be available on production cell phones.