Cisco's Wi-Fi Phone
Forbes.com has a quick look at Wi-Fi-enabled VOIP phone. If a company deploys it in more than one location you can take the phone with you, and it acts just like the phone on your desk. Calls across the country or potentially across the ocean can be as free as a call across the office. There's also plans to incorporate support for wireless phone networks.
But wander from your desk long enough and chances are high that you'll come back to a telephone with that red voice-mail light glowing, meaning you've missed a call.
Sometimes that's the whole idea.
The coolest voice ever.