Darren,
The one you linked to was the readout only, and it is the readout which gives you the bells and whistles. Depending on how much you pay, depends on what you get on the readout. The cheaper the readout, the less features you will get. A basic one will only handle two axis, say X & Y, then the next step up would be a 3 axis one, X, Y & Z. Then after that comes the features that the box of tricks holds. Things like auto off memory, where if you leave a job half way thru, you can turn the whole system off and come back to it at a later date, and when you turn back on, it is as though you had left it turned on all that time, zero point memory, where you can (on mine 200) store individual datum points that can be recalled at any time. PCD calculations, taper calculations, points along an angled line and the list goes on and on. It all depends what you want it to be able to do. Every function has a specific and very handy use to help make machining and measuring a lot easier. It can only be up to yourself if ever you are going to need or use that function.
Going by my more expensive version. At the press of a couple of buttons, my scale readout will convert to be used on almost any machine, be it mill, lathe or even grinding machine, or the accuracy of the readout, on mine, in imperial, up to five decimal points, or I could have it at two decimal points if it is a roughie job.
Everything depends on what you want to pay and what features you want fully automated.
For each axis you want to display, you will required a read head.
These start from about 100 squid each, but it all depends on the length and size plus quality of the read head. You can get big beefy ones where room is no problem, down to mini sized ones where you need to squeeze them into tight places. The normal size is the cheapest, larger and smaller work out more expensive.
If buying the read heads and displays as seperate items, you must ensure that the two are compatible with each other, both in signal type and plug fitting.
I searched all over the world for what I wanted, and also to match what my machines already came fitted with. I found a lot of cheapie types from the far east, and I think Cedge went that route and had very good dealings with one company, and the one in the UK who I dealt with was
http://www.machine-dro.co.uk/index.php?target=categories&category_id=3And I found them to be very speedy and efficient in dealing with orders and problems.
I hope this has helped you on your quest.
John