La puedes descargar desde aqui o usando QR Droid Private en la imagen QR debajo.
New App in Android Market
It's called Wi5. It lets you communicate to another android phones with the same app and make unlimited calls while you are in the same WLAN. This can be used as a Walkie Talkie where you have a WLAN infraestucture.
You can download it from here or by using QR Droid Private on the QR below