http://obse.silverlock.org/obse_command_doc.html#IsModLoaded
IsModLoaded is easy.
Adding the armor may be more difficult. You might have to use "runscriptline" since directly referring to anything from the other mod wouldn't compile.
Nice, thank you!
Anyway, I wasn't planning to directly add the armor from the mod(s), but rather I would create a new armor ID using the meshes from that mod (whether or not it is loaded), and have an NPC wearing said armor, but of course if the mod isn't loaded he'll have the invisible missing mesh glitch and stuff, so I would run the script before loading the NPC and if the mod wasn't active I would place a different NPC wearing Vanilla armor.
Anyhoo, thanks for your time; now that I know this is doable I will have to spend some time brushing up on Oblivion scripting and seeing if I can make something awesome

CC