The company at flow-rite.com has some interesting products. This is one of four different battery fill systems they have on offer. For those with lead acid batteries and a need to fill them up with water from time to time, this could be the answer
One of the primary causes of short battery life is a failure to maintain proper water level. Whether your batteries are in plain sight or hard to reach, adding water to the proper level couldn't be easier with the Qwik-Fill On-board Battery Watering System from Flow-Rite.
After a simple, one time installation that takes only a few minutes, you can fill all your batteries simultaneously from a single remote fill point without ever having to remove a single battery cap. You no longer have to touch or even see your batteries. The level in each cell is controlled independently, adding water only to cells that are low. It will not overfill and its precise accuracy would be almost impossible to match with conventional filling methods. Finally, the battery accessory we've all been waiting for has arrived.