what about adding status messages to the miners? For example if he hit the ground there's a message in there ( or on a monitor ) which says "Hit bedrock" or if he hit lava...
Why this idea? Because sometimes I don't know why he stopps, and then I have to dig down, check the pump etc. and take a look ( which is a bit annoying, because Miners are usually there too prevent this )
EDIT: Just wanted to add some examples. The status message can be like "Digged x blocks down / x blocks left", "Hit bedrock / Done", "Hit lava / water, pumping...", "Just found some IRON, taking it...."
EDIT 2: If it's not possible to use text (whyever), you can even use pictures like here (lava picture if hit lava etc.): http://i46.tinypic.com/2lm49py.jpg