The T815 has just a bit more features than the T805 -- but both fit in your pocket, have visual and spoken directions and points-of-interest location (like the hole-in-the-wall burger joint).

ENGADGET: Motorola T805 and T815 navigators: for most Bluetooth phones

On the other hand, for a compound eye to be effective, its elements must point in lots of directions, in order to cover a wide visual field.

ECONOMIST: Brittlestar eyes