Emby's device management is a little lacking in my opinion and could benefit from a few additional options that would make it more useful:
Under the devices panel the ability to actually specify what is a shared device or not would be awesome. Currently you cannot specify which devices are considered shared or not (DLNA is shared others are not..) This means that if you had a dedicated HTPC running Emby Theater (or any client really) you couldn't make it a shared device.
Under the user options there are currently two options "Control other users" and "control shared devices" I would like to see a third option added "Control only devices from local network":
This option would only allow the user to control devices that are in the same network as they are. Currently the server knows when a device is in the same network as it as it uses this for the "local pin" function. So anything that qualifies for the local pin would be considered to be in the same network. On the flip side any remote devices would be considered to be in the same network if they had the same IP since requests coming from over the internet would all appear to come from that network's router.
Its not really often that you need to control a device that you aren't on the same network. To make control of devices in my local network more straight forward both my girlfriend and I have the "control other users" and "Control shared devices" enabled however this means that we both can always see all the devices of our friends who are connected (which often includes an array of browsers all named identically) we keep both options on though since its annoying to not be able to change the video from one device or another because the other one is already controlling it. As an example: my girlfriend starts queues a bunch of TV shows [play all from here] then walks away turning the TV off since she changed her mind then I show up and want to watch something else but there is currently content playing already playing so I either would need to wait for it to finish hit stop on the remote over and over until I got to the end of the playlist that she had queued up to free the device up for my account to control.