The Live Mesh team recently announced that Live Mesh for Mobile is now available for all countries, so everyone can try it out. Since the mobile service initially launched back on October 30th, the team has updated Live Mesh for Mobile to address many of the reported issues that users had submitted. With those issues out of the way, the mobile version was then ready for wider testing. Although anyone can try Live Mesh for Mobile now, it is worth noting that it works better on 3G networks.
If you want to try it out, you had better hurry: there are only a limited number of spots available. To sign up, go here and add your Windows Mobile device to your Mesh. (That link will provide you a Live ID for adding a WM phone to the Mesh.) If you were already running the Live Mesh for Mobile client on your device, you should see an update notification the next time you log in.