In the ongoing saga of Ed vs the WOW Router, I've learned that necessity is the mother of invention.
Getting access to a network from the outside isn't easy. For obvious reasons, it's not supposed to be. But there are a couple of tricks, and of course, your mileage may vary.
The technical difficulties in this case are that the WOW router can't maintain a static DHCP assignment for my home "server". When the lease runs out, or the system reboots, it gets a new IP address. This means that port redirects are pretty much useless, so standard methods (vpn server, RDP) won't work. Also, the virtual server and port forwarding don't seem to be consistent.
Hosted solutions seem to be the only answer.
LogMeIn seems to be a nice solution, and it works well from a browser outside the network. Once the server application is installed on my server I can connect and RDP through a browser by logging into the site. The service itself is free for non-commercial use, but the Android client is expensive at $29.99.
Teamviewer is another popular choice. Just like LogMeIn, there's a desktop server application, and once everything is configured web access is easy. The Android app is free, but kind of klunky and it doesn't work well at all with a keyboard and mouse on my tablet. It's so bad, in fact, that it might be a deal breaker.
The last option I'm looking at is NeoRouter Mesh. Unlike the others, there's no web component, but it does provide a good vpn option and a portable client. The client will allow you to launch RDP or VNC clients after it's established a vpn connection. The downside is that it's not completely free, at $1 per license per month. I'm not sure that over the long term I can justify that.