 IP Web phones-These devices combine a complete analog phone device and a diskless processor, providing an e-mail browser and a variety of orga- nizer applications such as a call list and directory manager, a notepad, and a calendar. SIP phones-SIP has the potential to realize the ultimate IPT dream: low cost, feature-rich headsets from third-party phone vendors. SIP for VoIP phones is mature and solid, with at least six models passing the test. Major platform vendors continue to rely on propriety protocols for both their plat- forms and their handset features. This suggests that despite talk of support for SIP, complete openness and interoperability have yet to be achieved. However, vendors can test the interoperability of their SIP implementations with other vendors three times per year at the SIP Forum SIP IT events (www.sipforum.org) Mobile IP devices-This category includes 3G handsets, Wi-Fi SIP phones, PDAs equipped to handle VoIP, and game platforms. Chapter 9 IP Services In addition, the emerging generation of intelligent wearables, automobiles, smart appliances, smart rooms, and ultimately implants will all add to the expanding uni- verse of IP devices. IP-Based Voice Enterprise Systems There are three main approaches to IP-based voice enterprise systems: IP PBXs, open-source PBXs, and service provider solu- tions, which include IP centrex, hosted PBX, and virtual PBX services. IP PBX and IP centrex offer network management advantages over legacy PBX solutions. IP PBXs What can an IP PBX environment do that a traditional PBX can't? IP PBXs boast dozens of new applications, ushering in a new era of human communi- cations, productivity, and mobility. These enhanced and advanced applications are a very hot area, representing the potential for incredible revenue. Significant progress has been made in several key applications areas: unified messaging, which is defined today as the merger of voicemail, e-mail, and fax; conferencing applica- tions; collaboration applications; presence awareness; multimedia pack