Currently I use LogMeIn on all of our PCs and Macs for a way to remotely diagnose issues on them. This works great since it's very easy to get to the machines to matter where they are as long as they have an internet connection.
I will be deploying 20 Ubuntu machines that will travel weekly. The internet connection on them will be just a simple 3G WiFi hotspot, so the IPs will change constantly. What is the best way to accomplish being able to remotely access these machines with VNC or an equivalent? I would prefer a free option, but am open to paid services as well.