--begin rant--
An easier, safer and more humane way of dealing with a cat in heat that does not have any other outlet is: get it fixed!!!.
People who own animals that don't properly take care of them in all regards, including reproduction, should not be allowed to own them.
There are millions of wild cats simply because an irresponsible owner doesn't have the time to have them spayed or neutered.
--end rant--