iArrived
OS X app (10.7+) that detects iOS devices entering/leaving the local network - optionally showing a growl notification and playing an iTunes track.
I had a lot of fun writing this last christmas holidays, but ultimately it ended up being more of a learning experience than being practically useful – mostly because our office already has another network-based welcoming system in place.
Don't want to compile the project with Xcode? Grab the app from the Downloads page.
To use, all you have to do is check the "Sync with this phone over Wi-Fi" option in iTunes. Then open iArrived from your menu bar and follow the device.
Source-code provided as-is under the MIT License.