There are many problems with this approach. The first thing is it would wear a hole in the end cap at the high points of the switch. If one wanted to use that type of switch there would need to be a solid form to fit the contour of the end cap that would mate with the switch. This would prevent the end cap from prematurely wearing out. Another problem is the end cap needs to be secured to the tubing. They are too rigid for this and this increases the force required to actuate the switch. I’m not sure how well a piece of wood dowel rod would be accepted by my customers. Not to mention trying to source it. I’m not interested in cutting wood dowel rods to length for 1000 kits. 
I actually have some parts around here somewhere that do exactly what you have described, but no wood parts. The main problem is not destroying the switch in operation.
I have been thinking about this design for a while, and wanted to submit my 2 cents. While there is the possibility of mud and dirt bollixing up the sensor at the external location just above the foot pad, additionally my house has two very furry cats (of which one is Angora) Furballs are an obstacle that I need to consider, in addition to mud, dirt and dust! And there are these wild dust bunnies skittering about… 
The grounded connection concerned me as well. I have run into several power problems with shorts to grounded frames when mixing different power supplies…
This is my attempt to resolve these issues, based on Jim’s original design. Feedback is desired!
http://i590.photobucket.com/albums/ss345/djl02184/footswitchcutaway-dj.jpg
I have noted that the original contact point still provides a path to ground/power, but it could be insulated as well. I have successfully soldered to nuts before to create a power path. You can cut a notch in the side to lay in the wire for a neater connection. Additionally, the PCB contact disk can be pre-drilled for the wire, which would then be trimmed/filed for a neat connection (making sure that there is no contact from the rear to the HUB-08)
Cool ideas. When I get the parts it will be fun to experiment with different configurations.
Basically your design is the same as the original except you moved the wire to be internal instead of external. This makes the wire more crowded and I think can restrict movement or worse, potentially wear through the insulation causing a short. It might not be likely but it could happen over time. I think the original design is fine. You could use a spring inside so that it can contact in two places, at the foot and inside as well. A spring of some sort would be needed because once the foot makes contact the inside connection might not ever happen, or vise versa, the inside connection could prevent the foot from making contact. A spring/spring tab would solve this issue.
If the bot is going to be going through sand, mud, or any other substance that could prevent the foot from making contact, a soft rubber boot could be fitted around the foot and the tube to keep the contacts protected. Tie wraps could be used to secure the ends of the rubber boot.
http://image.made-in-china.com/2f0j00QvwtrsIqbEoN/Rubber-Boot-Rubber-Bellow.jpg
Any idea of the size of those things in the image? Source?
I’m not sure of the size, I just grabbed the image from google but here is the link that has these products.
Given that the part is listed under “Rubber Auto Parts”, I’m willing to bet that these particular ones are too large 
It’s a good idea though, we’ll just have to find smaller ones. 
Wow what a major pain in the… You would think it would be relatively easy to find a small rubber bellow with a 0.5" ID. All the sites I find call it custom. There has to be an off the shelf solution for this. When I find it it will solve all of the problems. I could even see this being pretty waterproof if done correctly.
This is hard to find.
This company in Ohio might have something that would work. The very top line of the list shows one that would have to be streteched over the tube by around 4mm, since the I.D. is 8.4mm when the tube is around 12.7mm but the maximum I.D. is large enough so that it would fit over the tube with a little room to spare which is good. It would have to be tested. It’s 35mm in length x I.D. 8.4mm min x 13.79 I.D. Max.
Hi Mike, good find there. I’m ordering some samples. 8)
Remember that how to pick up paper post in the arm section?
viewtopic.php?p=56165#p56165
Well they have a pretty wide range of off the shelf parts.
I think this is going to be a very good thing!
I agree this is going to be a great product for all those legged bots out there. I can’t wait to see the prototype assembled.
Looks like a little suction cup. Maybe now the 'bots can walk on the walls!
Alan KM6VV
Hahaha they want $12.00 each for those things!
I’m still waiting for a quote from Anver. I think it will be much better.
Thats crazy!
We could probably manufacturer custom bellows of latex for less than that… $11.95 anyone? Seriously, I do latex casting for my animatronics - the same techniques could be used here as well.
dj
A search for switch covers might also turn up some items. One also might cut the fingers off of some large latex gloves, and dip the tips in some of the liquid rubber like coating that is coated on tool handles. Red coating would make for some hot toenails 
Actually that might not be a bad idea. Not the dip in red stuff, but just the rubber glove. Cut the finger off, then cut the fingertip off, slide it up over the open area. The goal here is to prevent dirt from getting in, but not adding significantly the pressure required to engage the switch. I got a price on the Anver rubber forms. They are a lot more reasonable at ~$5.00. They are cool looking, but… Dang, $30.00 a set!
If you just want a dust cover, a round plastic shield would be easy to make from the plastic of a drink bottle.
Careful Jim, don’t get sucked into the Elmer’s glue arts and crafts engineering mentality. 
$5 is way better than $12 but you’re right, $30 a set is still up there. You need to find something for pennies on the dollar. The rubber glove idea is a good DIY solution but I think for aesthetics, a bellow type cover is more professional looking IMO.