I hope that radar doesn't detect monsters as well...
There are two coop servers (plus few others by loathsome I think, I only know the moocow one though).
The first server is classic coop, now uses ecoop which is enhanced coop by afcore, based on ccoop by Cardiologist(on the classic 3's coop server). It uses some new features, recently AFcore made changes to playerpawn so it can use weapons made under Unreal, so no longer online dependancy on tournamentweapon subclasses.
It also randomizes fatness and drawscale and collision of some enemies, making it a bit strange and there are the super gibs and stuff. (I found it a bit annoying at first but I got used to it)
Also provided are set of funny voices players can trigger and save checkpoint function and some HUD features you can enable (including radar, by default it is in protected mode, you can't see monsters behind wall on it, only within your range, monsters which can see you, with unprotected mode it scans all though). Yeah, kinda ruins the classic fun, but it is all optional anyway, you can enable and siable all these HUD features clientside.
The second coop server is akcoop plus monsterspawn stuff, using asgard's akcoop mutator and monsterspawn and lots of other weapons and stuff, really crazy.
Also the server is supporting more and more maps any day it seems, it grew rather fast over last year.
Last mappack that was added was Redeem your Space and few of UPSX map conversions and stuff.
Also all TVcoop stuff etc is supported, you can enter passwords in, you can crouch (without item), have footsteps etc etc.