Well on a USB stick anyway.
Here's the full lowdown from Realtechnews: http://www.realtechnews.com/posts/1890By Sean Fisher
Contributing Writer, RealTechNews
I still haven’t hopped aboard the VoIP bandwagon just yet, but this VoIP-capable USB stick from Mplat might make me think about joining the ranks. The F2K not only allows you to make calls from any PC with internet access (without having to install anything), the flash device also has the ability to store your chat records for you.