Hampton Software released VoIP software called Articulation for PalmOS with the following features:

- Ability to make PSTN calls with your PDA
- Select the SIP VoIP provider of your choice
- Lookup phone numbers direct from you contacts
- Touch-tones (DTMF) for ‘phone menus’
- Supports WiFi, Bluetooth and EVDO connections
- Call timer
- Silence suppression (only transmit your voice)
- Echo cancellation for ’speakerphone’ use

Via Voip Blog