Reference: www.screenconnect.com
We recently purchased two licenses of this to handle our remote support. I have since installed the "Access" agent on about 75 client machines. This software just rocks. I upgraded 7 desktops and 2 laptops from Windows 8 to Windows 8.1 this week all through ScreenConnect.
It is $300 per simultaneous technician needing to be connected for 2-4 and gets as low as $250 per tech when buying 10+.
Pricing: http://www.screenconnect.com/Purchase
Their upgrade pricing is also one of the fairest things I've seen.
Upgrades: http://www.screenconnect.com/Upgrade
Meetings and support sessions all support audio through the app itself (mic/speakers required of course, duh!)
The product has been around since late 2009 going by their press releases. If anyone is in the market for a remote support tool, I will highly recommend it.