What this is talking about is effectively extending your home network to a remote location. Once you have access to your home network, you can (in theory, anyway) do anything you would be able to do if you were on your home network... broadband bandwidth permitting.
Clearly there are security implications in opening your home network for external access. One way to do it is to use a VPN (virtual private network), which creates a secure (encrypted) bridge between two local networks over the Internet.
The other way is to tell your router to allow external accesses it would normally block, and then (with some jiggery pokery) you can "dial in" using your external IP address. As the typical home user does not have a fixed IP address, you either have to pay to have a fixed IP address (private domain), or you use a service to track your current IP address (dynamic DNS). Whether you fix your IP address or use a dynamic DNS system, you have to open your router for specific kinds of access and if you are not very careful you are opening your home network to attack (don't believe it won't happen – there are automated systems probing the entire Internet for vulnerabilities, which our routers normally keep out).
all I get is twonky media or media tomb
I guess that means you only have the DLNA service ports open through your router. Different digital services (eg web browsing, email, whatever) use specific channels known as "ports". They're given a port number. The router lets through particular services, and messages with a specific port number are only allowed to do the things normally associated with that service. This is how the router can stop incoming threats. To get external access to other services (eg WebIF access) you would need to tell the router to allow through those particular service numbers, ie ports. If you are going to allow external access to your WebIF, it is highly desirable you set up https or at least passworded access (if those are available on Foxsat). The links below will explain the details.
Security-wise, you would be well advised to use a VPN. It's not a question of whether you have anything to hide or that nobody will be interested in your recordings, it's a question of what nasties might get planted on your computer systems (and the Foxsat is just another computer) - spyware, DoS attacks, botware...
I have never had the need nor desire to do any of this, and my uplink speed would make video download impractical, but all this was discussed some time ago for HDR-FOX (and Foxsat would be no different). Bearing in mind the following info is for HDR-FOX: