Short list of features:

• Use industry standard VoIP telephones available from Digium, Polycom, Snom, Cisco, or traditional analog telephones
• PBX is economically sized for a few telephone extensions and up to 400 extensions
• Create remote extensions for staff that are located at a remote office or mobile
• Toll free calling to all remote extensions anywhere in the world (internet required).
• Easily manage all your calls
• Powerful interactive auto attendant
• View caller profile information with photo, extension, title and location when co-workers call
• Use Switchvox's built in chat server to quickly connect and chat with co-workers.
• Allow each user to create custom phonebooks with custom grouping.
• See detailed up-to-the-second data on your call queue.
• Integrates with Google Maps to show where the caller is located.
• Crystal clear call quality with HD voice.
• High reliability software finds redundant call routes of the primary is down.
• Digital faxes allow you to send and receive faxes from your computer.
• Record calls and save them for easy retrieval
• Listen in on calls, with the ability to jump into the conversation if required.
• Know whether or not a co-worker is available before transferring a caller.
• Simple and powerful conferencing option.
• Switchvox mobile allows you to use the power of Switchvox on your iPhone , Android and BlackBerry Smartphones
• See your caller using video phones and video conferencing equipment
• Much more! Call us for complete listing.

Digium's Switchvox Feature Page (PDF)
Digium's HD Voice IP Phones (PDF)
Siemen's Gigaset A580 IP Phone - datasheet (PDF)