A computer shouldn't pose a problem at all. All the parts for it are on the front half of the bike and very small so should not in any way affect the folding mechanism.
The way a 'puter works is with a magnet you affix to a spoke on the front wheel; this goes past a sensor you fit on the fork that records each revolution of the wheel and sends that as data to the computer which you fit to the handlebars. It in turn converts the clicks into useful data like speed, mileage, averages etc.
On mine I opted for a cabled version to join the sensor to the computer as I was a little concerned that the distance between them might be a little far for a wireless model (which is probably designed with a bigger wheel in mind) which in my experience are harder to set up (you have to make sure they are in line vertically and it's all a bit intricate. Other people may have had success with wireless - it's certainly neater. I just wanted to play safe in case it didn't work.
When you get one - be sure to key in accurate data about the circumference of your wheel to get the best readings. I could have just set mine to 20" for my wheels but I opted to roll the wheel along a tape measure and work out the exact distance one revolution takes and put that into mine. FYI my 'puter is a Cateye Velo5.
Hope that's some help.