Here's your end product. Pretty nifty eh?

This is not a project for the faint hearted. You're about to destroy a very expensive pair of trainers/sneakers and have to problem solve along the way.

Step 1: Suitable Trainers

Get yourself some trainers (sneakers, to those of you who're not English) that have bubbles in them! I chose some Nike active airs because they are not shy with their bubble-to-trainer ratio.

You are going to destroy the active air principals/function of these shoes, you have been warned.

Step 2: Make Sure You Can Remove the Innersole

You'll want to get down to the padding of the shoe that sits above the bubble area. These trainers come with a removable innersole - handy.

Step 3: Tools

You'll need a knife, some small pliers and a mini (dremel) drill.

This is VERY DANGEROUS. I managed not to cut myself at all, but seriously be careful. You're putting a lot of pressure on a knife in a very small area with your fingers in the way. Make sure your blade is sharp, I used two blades for this process because they blunted so quickly.

Step 4: Cutting Away

I drew around my light unit on the lower innersole of the shoe. I then cut away the top layer (the grey bit you can see here) to reveal the under layer, which had a membrane and then colourful rubber padding.

If you cut the edge line first and then start working on the middle section you'll be able to pull away larger chunks at a time.

Cut a little section partly out and then hold it with the pliers while shearing away underneath it to remove more.

Step 5: Keep Cutting

You'll be down in the padding of the shoe. You'll need to cut a little hole for your light unit to slot into the bubble area.

This will puncture the air bubble and make the trainers slightly softer to walk on. Who cares! It looks awesome.

Seriously though: don't cut your hands doing this!

Step 6: Smooth Your Cut Area

Sorry! I forgot to take a photo. Needless to say I got orange and purple rubber dust EVERYWHERE, but it was worth it.

Problem: if the area underneath is not flat you can lose connection between your lights and their battery pack.

Solution: cut up old credit card to act as a flat support for the battery pack & put bathroom sealant as a flat layer on the bumpy rubber layer once the smoothing was as smooth as possible.

Step 7: Add Your Lights

I got this light unit out of a kids pair of trainers. I could have made my own circuit but I was feeling lazy by this point and had these units kicking around.

They're much bulkier than my own circuits, but they do the job.

Step 8: Putting Your Lights In

If you've got a switch and removable battery pack like me you'll want to make sure these don't move with your footsteps. Else you'll end up turning your lights on and off without meaning to!

I glued them in place and used a cut up old debit card to act as a platform for the battery to sit on.

Once your glue is dry add the battery pack in, put the upper innersole back in and get ready to revel in how awesome your feet now look!