iTwin from iTwin Inc. is a rather unique product and one for which a certain population will probably give thanks. It lets you move work back and forth between Macs and Macs, Macs and PCs or even PCs and PCs. The iTwin is secure and it fits in your pocket.
iTwin
iTwin supports Win XP, Vista and 7 as well as Mac OS X 10.6 and above. It requires broad-band internet access, 15MB of hard-disk space and a USB 2.0 port. The supporting software must be loaded on each machine where iTwin will be used. MSRP is US$99.99.