Ever tried bleeding brakes by yourself? It's a pain in the butt. This is simple to make, and makes the job simple.
Small rubber hose, to fit over bleeder screw (1/4"-ish)
Larger rubber hose, to fit over small hose (1/2"-ish)
Small marble/ball, should fit inside large hose, but not small hose
Spring, same or smaller diameter as ball
Step 1: Assembly
Slide the large hose over the small.
Line up the spring, ball, and another piece of small hose alongside. This will give you an idea of how long to cut the large hose.
Cut hoses to length, make sure the small hose that the ball is going to seal against has a nice smooth cut.
Wedge everything together far enough to partially compress the spring. With any luck your hoses are a tight enough fit to hold themselves.
Step 2: Usage
Before putting the hose on, make sure you can get the bleeder screw loose. I just left the wrench on the screw and put the hose on after that. My hose wasn't a real snug fit, so I put a clamp on it. Put the hose into a bottle or pan to catch the oil. Open the bleeder screw, and go pump away at the brakes.
With clear hose you can come back and check whenever you want. If there are still bubbles in the oil, go pump some more. If there aren't any bubbles... Give it another pump or two for good measure, then tighten up the screw and pull the hose off. You're done, wasn't that easy?