Linksys has launched the WIP300 and WIP330 wireless-G IP Phones. Regarded as first in line of Wireless IP telephony products from Linksys, these phones would enable callers to make low-cost VoIP calls through 802.11g wireless networks.
These were the features of the phones which I found at geekzone:

Features of the WIP330 include:

• Support for SIP v2 standards
• Compliance with IEEE 802.11b/g standards
• 2.2-inch color LCD display
• Support for Quality of Service (QoS)
• 3-way conferencing, call hold and resume, and caller ID
• Fast Hotspot Authentication
• Support for auto-provisioning using HTTP or HTTPS for configuration and upgrades

Features of the WIP300 include:

• Support for SIP v2 standards
• Compliance with IEEE 802.11b/g standards
• 1.8-inch color LCD display
• Call forwarding, call transfer, call history
• Backlit keypad
• RF and battery level indication
• WiFi survey tool
• Connection status button
• USB charger interface
• WiFi Phone Requirements

One of the interesting facts about these phones is that they have all those features that one finds in a mobile phone such as customizable ringtones, phone book and wall paper. The entry level model WIP300 retails at $219.99 whereas the higher end model WIP330 is a thin and sleek model and it retails at $369.99. One thing, the flip side of the WIP300 is that it does not work at hotspots which require credentials.