pttdroid

pttdroid is a Push To Talk VoIP app for the android devices witch can be used in WLANs.

https://sites.google.com/site/pttdroid/

Screenshots: 

Application Permissions:

Internet- Allows applications to open network sockets.

Record audio- Allows an application to record audio

You can download at: http://apk.cuaban.net/detail/9820/pttdroid.html