The wired ones are simple to connect to a small mill and will be a lot cheaper than the full wireless systems. You don't need any special interface either, as they are normally closed contacts and can usually wire directly to your controller.

The mounting is also simple. You can make up your own holder from a generic toolholder. They have a hardened ball as a pivot and 3 (4?) machine screws for adjusting runouts, so you don't even need to be very accurate with your machining. Note, you will need a DTI with a very low contact force (ie less than the probe) for adjusting runout.

Keep your eyes on ebay and you should be able to find one for under £200. I nearly got one for £50 a week ago but got pipped while I was in a work meeting. Gah!

Renishaw probes are so much better than homemade / Chinesium ones and are going to be more accurate then our machines will ever be.