Here at Instructables HQ on San Francisco's Pier 9, the men's restroom had a problem.

Particular pier peers persist as poor-precision pee-ers. The result of which is photographed above. (Emphasis added).

Solution: Positive-peer pressure for proper peeing posture. The Urinal Spash Danger Meter

A solar powered electric apparatus for displaying pee-stance quality* and correlated splash risk.

The concept is explained in this excellent video.

*Pee-stance qualityis directly proportional to distance from urinal. Closer is always better.

Step 1: Aquire Parts - Begin Tuning

How does it work?

It is deceptively simple. It is just a solar panel and a analog meter. The more light that hits it, the more danger it indicates. The closer a person is to the meter, while properly lit, the less danger it indicates. Being solar, it requires no batteries or plugs.

Meter/Panel Selection

This is a somewhat difficult process. I got lucky and had a bathroom with a strong directional light source directly above the users head. Because of this, a stark shadow is cast on the solar panel which causes the needle to drop. I do not know if there is a good reason to use a ammeter vs a voltmeter, as both increase as light increases. I was more confident in an ammeter as I was getting noisy results on voltage.

Start with a solar panel and a multimeter that can measure amperage.
Measure the current on a panel in a dynamically lit part of the bathroom.
Note the amperage both with bad urinal posture
Buy an ammeter that approximately goes to the high limit

Note that if the difference is smaller than 20 microAmps, you will need to either get a bigger panel or change the lighting in your bathroom. I have not been able to find any analog meters that have precision less than 20 microAmps.

Once you have your parts on hand, hook the panel up to the meter. Red to + and Black to -. You should have immediate response to changing light levels. Find a place on the bathroom wall that works with your parts.

My Parts list:

Note that your parts may differ, as your restroom is non-identical to mine.

Black Acrylic Sheet 0.118 Thick 12 x 12 (We will cut it in a later step)
50 microAmp Ammeter/Galvanometer (Analog)(eBay)
Small Solar Panel (I used a RadioShack I had on hand)
3M Dual-Lock

Step 2: Design the New Meter

The μA label is not going to cut it if we want people to know what is going on. Time to make our own!

The finished files are attached, so these steps are only needed if you want to design your own.

Making Template

Take a nice straight-on photo of your meter
Measure the original label width
Bring the photo into Adobe Illustrator or similar and scale it to be the exact size that it is in realit
Put that photo on a background layer and lock it so you don't accidentally move it around or scale it
Optionally, you can print at this stage to ensure your scale is accurate

Designing Gauge Face

In order to make this thing look official and sciencey I decided to use DIN, a nice german font. After a lot of thinking and math, it was determined that the scalar quantity being measured by this solar apparatus is μDroplets/cubit² (microdroplets per square cubit). The meter reads in a exponential fashion, with an asymptote at infinity. Demarcating the danger zone requires testing your panel and your meter ahead of time. I got lucky and had a pretty even spread.

Draw a circle around the pivot point of the needle until it crosses the existing tick marks. (Hold Alt-Shift on the Ellipse tool and drag out)
Open the Stroke menu and increase the stroke width for a thick bar encircling the meter. I used 11pt.
Still in the Stroke menu check Dashed Line. Make the Dash about 8pt and the gap an absurdly large number like 1000pt. This gives a partial arced bar that can be easily resized and colored.
Make the Stroke green and rotate it until it is lined up with zero on the original meter.
Copy the circle, paste-in-place, and repeat for Yellow and Red.
Use the Text on a Path tool to write CLEAR and DANGER
Use the Text on a Path tool to write the numbers for the tick marks.
Add logos and labels
Print it out, trim it with an X-Acto, and see if it fits. Minor adjustments will likely be needed.

Trim and glue

The design can be cut out of regular printer paper and glue-sticked to the old face. Simply force the cover off the gauge and slide the sticky print behind the needle. Once set, reassemble the gauge.

Step 3: Design the Plastic Chassis

The meter needed to be mounted on something. A project box would have worked too, but I wanted something sleeker. There are thousands of ways to do this, and I'd love to see how others solve this problem in the comments.

I decided to use black acrylic plastic(Plexiglas) as it is easy to heat bend and easy to laser cut. Don't have a laser cutter? Don't fret. Simply print the stencil and drill the holes. There are two components and they can pretty much be mounted to anything.