The list is long, there is not really a limit to what you can usr to train for climbing. Anything heavy can be used to train grip strength, or can be attached to body to do weighted pull ups. And if you cant start drilling holes in your walls at home, manufactures such as Metolius or Problemsolver have developed portable hangboards or juggy holds hanging off a piece of rope. These can easily be mounted on a tree branch or anything else you might find that can bear some load. Then there are lots of non climbing specific tools you could use to train general body strength.