The screen flickering trick also only worked on CRTs under Windows 3.1/9x, so if you had a laptop, any other system with a LCD, or were running NT you had to get a special dongle that hooked up to your serial port and would blink a LED that you had to hold in line with the watch's sensor.
Very magical to hold your watch up to the CRT monitor, see the monitor go black and flash a bunch of white lines for a few seconds and then look at your wrist to view the downloaded info.
But it was only letters and numbers so the routine got old fast.
Could be a bit finicky to get a successful transfer as well.
And transfer bandwidth was pretty low.
IIRC it didn't work with a CRT using MS operating systems after Windows 2000 due to driver changes or something.
But Timex also a sold little single-LED blinkenbox that plugged into an RS-232 port that would do the trick. That was intended for computers with LCD screens like laptops, but it worked with later operating systems too.
https://www.youtube.com/watch?v=A8ig2UPjOXQ
... The DSI e-BRAIN is also fully working in timex_datalink_client, which amuses me so: https://github.com/synthead/timex_datalink_client/issues/111