That is a Nokia N800. Another way you could use public WiFi… Its not just for coffee shops and laptops anymore! This video demonstrates the Nokia N800 tablet using Gtalk to make a video call to someone. Pretty good quality for a small device.
The popular VOIP software Skype works on the N800 now. This means you can send and receive voices calls from this tablet to a landline or mobile phone. All via WiFi.