Well, many posts so far, but none seem to hit the mark completely.
I am still relatively new to a dry suit, and on my first pleasure dive in a dry suit I had to thumb the dive early to answer natures call. It was at this point that I decided I needed to do somthing.
I looked at pee valves, and may eventually end up with one, but not for now. Huggies #4 came highly recommended, choose the most outlandish art work possible. I decided on male incontinence pads, they are simple and not very expensive. They have an adhesive strip so you just stick it to the inside of your underwear in the right place. I usually put it on at home when I am getting dressed in the morning. If you don't use it one will last all day. I throw a few into the dry suit bag for spares.
As far as testing it goes, put it on and wearing only your undershorts, stand in the shower and do your thing. Look for leakage and learn how to best positon the pad to prevent leakage. Your urine gets into the pad and turns to a "gel" so there is no liquid to possibly run down your leg, the layer of fabric next to your skin remains dry so there is no "wet" feeling. At worst it feels a little clammy. For your underwear choice I would think, briefs will be better than boxer briefs, and boxer briefs would be better than boxers. Keep the pad close and in the right place.
When you go you will need to change the pad when you are back on the surface. I would recommend only ONE use per pad, if you get my meaning. The incontinence pads I use come in a white plastic wrapper, I place one pad in a sandwich size zip lock bag, when I need to replace a used pad I put the used pad in this zip lock bag and into the trash and put the fresh pad where it is needed.
When you are deciding on the best placement of the pad, remember, when you are diving you will most likely be laying face down not standing up, so put all of the "parts" in place with this in mind.
All solutions to this problem can fail, diapes or pads can leak, condom cathaters can become blocked and "blow" off. I think the incontinence pad is a cost effective and low bother solution. It allows you to fully hydrate with few worries, just "go" dive.
Mark Vlahos