I think maybe this is a very recent block addition, I can't actually find any information on it. It seems straightfoward enough, but I can't get it to work. Most notably, when I click on the Filter configuration I get a grey box with a Close button and nothing else. So I can't configure the detector to really do anything.

Can you give me a screenshot please. Sounds like it may be broken. Also which one are you using? there are 2 tiers

I have a same situation. Here is the entity detector's configuration GUI.

The advanced entity detector looks like fine, but I clicked the +enitity button, I've got crushed...
http://pastebin.com/8WWWhsH7
I'm using All the Mods pack with Draconic-Evolution-1.10.2-2.0.3.137.

Both these issues should be fixed in the next update.