Typically people use an MPG (manual pulse generator) pendant to do manual axis jogging, however the ones that I have seen use a USB interface which must be connected to the PC (and used with the Mach3 software or equivalent) to work. In such a case, Mach3 would provide the DRO (digital readout) capability on the screen. So that approach does not meet your objective of not having to use the PC. A google search on "MPG pendant" should return some examples.
As an alternative, if you have some electronics experience you could put together an MPG pendant circuit that would directly drive the Keling's step and direction and enable inputs for each axis, either by swapping the cable from the PC to the breakout board with the cable from the pendant, or by building some kind of switch box. You could then either use the pendant in conjunction with a bolt-on DRO (which could be anything from cheap iGaging readouts to more precise but also more expensive glass scales and readout), or you could try to get by with a simpler but less-useful step pulse readout such as the one that you linked to, either as a standalone unit or built in to the pendant.
It is possible that someone manufactures such a standalone MPG and readout, however I have no direct experience with any such device.