The Aikron A30 DRO (and whatever scales you get, glass, magnetic and whatever resolution) has feed rate, spindle rpm function (comes with sensor), up to 5 axis (w/axis summing), touch probe input and the RS232 (not sure what this is for). You do need to order what functions you want when you select it as there are so many ports (6 maybe?) so you can only have to up so many inputs. I haven't use it much yet, but the A30 dro from them, the heavier duty display unit seems like it's very high quality, not metal, but heavy duty... we'll see how it holds up over the years. They have an A30P, cheaper plastic, same display/functions, but why cheap out.
From this an other posts, I may sounds like I work for them or get a kick back.. I don't, just found it to be a good value and sharing this info. Time will tell how I like it, but so far, I have zero complaints and glad I went this route. I wish PM provided a few more custom options in their dro packages. I really wanted the 4 axis for z and quill movement (though, in reality, not sure how great that is), a separate scale on the quill is just as effective. I think in the end for a 4th axis, with rpm sensor I was around $800 shipped.