To people who haven't worked in labs:
First off, generally the issue isn't tracking usage for the purposes of billing, or actual inventory (ie preventing people from walking off with things.) Most expensive stuff can and is plated and then cabled down to tables. The issue is often more tracking down who screwed up something so they're told not to do it again/given additional instruction, or their lab/PI is billed for the repair.
Why? All manner of equipment isn't cleaned after use, or toxic stuff is used on equipment that can't be cleaned of it easily, or equipment that is shared with other experiments that would be damaged by certain chemicals or contaminants. Centrifuges have the wrong rotors installed or mis-balanced loads, destroying the bearings or worse. Cryo vacuum traps don't get cleaned and can accumulate liquid gas and explode. Microscope objectives get damaged from impacting the slide or overuse of oil for immersion objectives. Microscope light sources get left on and burn out (some of them have lifetimes measured in hundreds or a few thousand hours.) The list goes on.
You can't always control power, because a number of instruments have long warm-up times before they stabilize, or require a bunch of parameters be entered on power-on.
Access control via keycards works until you discover that someone left the lab, dropped off their ID, security for some reason never cancelled their card, and now it's become a shared resource in the lab. This happens so often it's not funny, except in places that take access control VERY seriously, like hospitals that have research groups. Or people swipe others in.
It often really comes down to solving people problems with people, not technology...and having a culture of following procedures and policies. If someone can't follow procedure, lies, cheats, etc - they're a liability/danger to your lab/center/school reputation because they could be (and probably are) doing the same thing in their research. Why are you still employing/collaborating with them? Kick their ass to the curb.
That said, a lot of equipment manufacturers could recognize this need, and provide lockout contacts that can be interfaced with various access control and logging solutions.
Lastly, a reminder to Slashdotters: please think critically about the solutions you offer. If some random guy can think up a "solution", then chances are it's occurred to, and maybe even been tried by, someone with actual experience. At least recognize that possibility...