Needs, directional antennae, Another way to make this device with a little know how is the thing called nike+ it goes in your sho, cell phone not required, and a couple of arduino style gadgets. Presto blamo, a unique digital key already in your shoe, well in mine, and away we go, never have to carry keys when i run again. i saw this on Absinthes JB site, the lockitron, the other day, way cool.