I have been using Google Voice and I can see why a desktop application would be popular as there are mobile phone applications for the I Phone and Blackberry so 
why not the desktop. You can configure your phone number different ways. I have mine configured as a place to leave messages right now but have had it forwarded to both my cell phone and landline. This is what mine looks like now, no following:) This works for me though as I love getting the “transcribed text” message. This is what made me think about doctors with using a cell phone, get a transcribed message from the patients on the phones. It is not perfect but does pretty good.
You can send a text message back. The reason I use no following is so I have a number where people can message me if not urgent without ringing the phone. Also there’s an option to use Google Voice as a replacement for your cell phone carrier voice mail, and that works great too.
No more lost messages as you have a back up on your computer/web.
Below is a message from my Mom, who dictated the voice mail and Google transcribed it. Now once you are on the computer you can forward that voice mail to someone else or embed it on a web site, obviously user discretion here by all means. Doctors could occasionally find this useful with emergency type situations to relay information. As you can see on the web there’s no phone number listed as to where the message came from. The message can also be downloaded in an MP3 format, so lots to do here.
I really like the transcription services as I used to pay for this with other software and now it is free.
Again instead of that old pager a doctor may carry around, why not get your messages saved in this fashion. If a message is accidentally deleted, it’s backed up. No wonder everyone wants a desktop application for Google Voice and I’m happy with it. When I signed up on the beta I probably didn’t use it as much as I should have but now am in high gear.
You can use the Google Phone number as one universal phone number to give out and by contact determine which phones to forward to as well, so good way to perhaps keep family and friends close while sending others directly to voice mail if needed. Having the site open makes it easy to send a text message anywhere too.
This is also interesting as you can type in a phone number, select which phone you want to use and Google will do the rest, call the other party and connect with your selected phone, home work or cell phone. I tried this one out and it works well.
I think Google Voice is a winner in my book and so far have had no problems or issues at all. BD
Thousands of Google Voice users have signed an online petition asking the search engine to release a desktop application that would enable them to make telephone calls over the Internet.
The petition, posted over the July 4th holiday weekend, was started after the blog TechCrunch reported that the company was testing a voice-over-IP desktop app internally. The site, however, reported that Google may scrap the project because founders Larry Page and Sergey Brin want all applications from the company to work from inside a browser.
Google Voice today primarily offers call forwarding, voicemail, and a voicemail-to-e-mail transcription service. The service, which is available at no charge, was made generally available last month and has more than a million active users.
Google VoIP App Draws Petition -- Google -- InformationWeek