In DCC, the rails are constantly energized; you send a digital signal to the loco to tell MIT how much of that power to send to the motor. It's a fairly simple concept to have a base station wired to the track, and wireless handsets to send signals to the base station.
On a DC layout, locos are controlled by the voltage and polarity of the power sent to the rails from a powerpack with a rheostat. There is no commercially available system that I am aware of that will do the same thing wirelessly. The technology DOES exist, though. I have a home automation that lets me control dimmable LED bulbs through my smartphone. I'm sure it would be possible to adapt this technology to do the same thing for a DC power supply, but it would require a pretty high degree of electrical expertise (more than I have), and it would be expensive enough to make DCC conversion cost competitive. But you could do it if you so chose.