I just subscribed to a EVDO data service, so I can use a laptop and have internet access wirelessly. The USB dongle works out of the box on my Macbook with some configuration help I found here. On Windows, it's the typical installing driver and setting up a dial-up connection. Now that everything works, the fun begins.
I want to access my iMac from my Macbook over EVDO. Luckily, I have .Mac (MobileMe), thus there's back to my Mac. Despite plenty of horror stories about Back to My Mac, it just works for me. No need to deal with port forwarding and stuff. The only thing I find is that I have to enable Back to My Mac on both Macs, not just the one I'm trying to get access too, despite Apple's description on System Preferences. It works, albeit sluggish since Screen Sharing transmitted all OS X's eye candy, including all the dock animation, wallpaper, etc. Unfortunately there's no setting to reduce the quality setting.
Now, how about Windows? I want to see if I can access my XP Media Center PC from an XP Home machine over EVDO. Microsoft offers Remote Desktop Connection, which is free (vs the paid service of MobileMe). However, with XP, you can only setup remote desktop connection to an XP Pro or Media Center (On Vista, only Vista business and Ultimate, another reason why I recommend people NOT to get Home Basic/Premium). You can, however, use any OS that is compatible with the Remote Desktop Connection software as the client. I've been using RDC to control my Windows PCs from my Mac. Combing google, I found a way called Remote Desktop Web Connection. The idea is you use RDC within IE, useful for doing remote desktop on any web-enabled PCs with IE. However, it involved installing IIS web server on the remote machine, which has security concerns. I tried it, and I can never get it to work. Silly me, I forgot about the Remote Desktop Connection client software that already comes with XP Home. I thought it only works only on local network, but it actually works over the internet too! If you're behind a router, you have to forward port 3389 (the default port, you can change it) to the remote PC. It works if you only need access to 1 remote PC. I haven't figured out what to do if you want to access more than 1 PC.
So, everything seems to be fine and dandy, until I found this article. This article is a great read to secure your remote desktop connection (forcing encryption, limiting users, etc). The only catch is when I removed Administrators from the Local Policies-User Rights Assignment, I couldn't log-in via RDC anymore. I have to add the username directly on that policy list, despite having the username already on the Remote Desktop setting screen. Remember, enabling remote desktop means you're allowing outside connection to your PC, thus increasing the risk of attacks.
So there you go. Setting up RDC on Windows is not as simple as Back to My Mac, but it's free, so can't argue with that. Another point for Microsoft RDC is that it can adjust the quality setting of the display by disabling themes, wallpaper, and other screen effects for more responsiveness. RDC over EVDO is very smooth, only a bit laggy, in contrast of the sluggishness of Apple's screen sharing. Back to My Mac is dead easy to setup though, and I believe it is more secure, as long as nobody knows your MobileMe login and password.