I hated always crawling under the tree to
a)Check whether or not I needed to add water
b) checking to see when the water resevoir was full
SO, let's make something that will help us with both!
All parts printed in PLA. Printed the battery holder and float support in black.
Float Switch that signals at the top and bottom of its travel
2-cell LR44 holder: http://www.thingiverse.com/thing:1134235.
Heat Shrink Tubing
The wiring was pretty simple, since i planned on using the coin cell batteries (LR44); no resistors! I used a NO switch between the batteries and the LED to minimize power usage and not drain the batteries. I soldered and covered all the connections with heat-shrink tubing. I didn't really secure the wiring to anything inside the funnel's recess; I just shoved it all in there, so I could easily change the batteries as needed.
The wiring was simply cable tied to the extra dishwasher tubing I had laying around. Simply feed the tube down the tree, snap the holder onto one of the tree stand screws, and VOILA! I no longer have to crawl under the tree!
A bonus is that my kids like to water the tree now; how about that!?