I'm looking to get one, just MPH and overall distance, cheap, and easily removeable. Any suggestions?

They all work pretty much the same. Just get the cheapest one on nashbar or something:
the cheapest
that one doesn't include cadence, but I guess that isn't so much a factor on a single speed.

order today and it looks like you can get free shipping...

Unless you just want one of the $10 rigs, it's worth getting the $30 basic wireless ones. Easy install, clean look, no wires to mess up, and you can put it in your bag or pocket and have your distance and average at the end of the ride without the numbers staring at you the whole time.

I've used this one for a couple of years, on about 5 different bikes. No cadence, but a neat "distance day" feature that tells you how far you've ridden that day. Great for us nimrods who always forget zero out the computer at the start of a ride.

Don't buy a schwinn one from Dick's, personal experience. I popped out and got run over.

I use one of those Cateye Micro Wireless that you can get on eBay for $20. It's cheap, waterproof, easy to program, etc. Like the others, no cadence, but I think the cheapest wireless cadence computers run $100+. I would personally recommend this computer highly.

In my experience wireless computers are very sensitive to electrical interference and aren't accurate at all in the city.

I like VDO computers, simple and bombproof.