If you have an Arduino project where the dev board is stuck inside a machine, or attached to the rafters or is inaccessible in some other way, a wireless programming/debugging link will save you tons of time. This tutorial is an extension on Rob’s version. In this version, no extra firmware or hardware (other than a capacitor) is necessary. Just use the default bootloader. I demonstrate it with a ‘classic’ Arduino but of course this can be easily adapted to any version or clone.
Wireless Arduino programming using XBee’s - [Link]