... and how do you call it?

Not really. The PC was never intended for real-time operations, despite of attempts to use it as so.
In fact, the ISP bit-bang (especially with the support of properly designed buffers) works most of the time on most of the computers in most of the configurations mostly correctly even on WinXY; but that's not exactly my point.

A professional programmer
1. makes it sure that it will work, rather than coincidence
2. adds value (safe operation (EMC), easier operation, ruggedness, mobility, anything)

My point with the box is, that with ISP the workbench is not the only place where device programming is performed. You need to provide the technician who is going to do the field reprogramming some hardware. And for field reprogramming by less qualified personnel (technician), who is doing more mechanical repair than electrical (and that is usually fixing wires), I would prefer a rugged 1-button box rather than a fully equipped laptop.

I think you know what I am talking about - you mentioned quite recently that you are seeking for people to replace a few socketed chips at various sites. Now imagine it's not about socketed chips but ISP programming.

Jan Waclawek