If you have an iPhone and have been frustrated about the solutions available to link up with Office Communications Server 2007 R2 (OCS) then wait no longer (video link below). Modality Systems has created iDialog in the Apple App Store for you at a price of $9.99. While many are shocked at the initial cost, if you weigh the options available from other vendors, it seems somewhat reasonable.
If you have an OCS 2007 R2 Communicator Web Access server you're all set. Typically when we set up these systems we have a split horizon DNS infrastructure so the server URL is the same if you're on the LAN via WiFi or over 3G.
In terms of feature set, most of it is there; just no conferencing (IM), application sharing, or voice callback. The buttons on the bottom of the application show "Contacts", "Chats", "Me", and "Settings".
The Contacts section shows your groups and takes about 5-10 seconds to appear. Each contact is selectable and will show Activity (presence), Calendar, email address, Title, Company, and various phone numbers based on your access level with them. You can tap to IM the person from the same screen. You can also tap a phone number and have the iPhone call them directly.
The Chats section shows any existing IM conversations you're having with people. It is important to note that when you hit the home button, the application doesn't stay running in the background and any conversations will be lost.
The Me section shows your Activity (presence), Note, Location, and phone numbers.
Lastly, the Settings section allows you to enter or correct your authentication settings. You need a domain\username, a password, and the URL to your CWA server.
So far I've found a few bugs with the grouping of IM contacts. Some contacts from other groups show up where they don't belong. Not bad for version 1.0.0 though :)
VIDEO: http://files.me.com/jasonshave/n10xuf (taken with an iPhone 3GS)