A few things I use, though not all are all that cheap...
This would be for team viewer type play, wherein a dom controls the sub's computer.
1st is a USB controlled power strip.
https://www.amazon.com/PwrUSB-Basic-controlled-Automation-automatically-remotely/dp/B008AZW9P6
Essentially, now your dom can turn on/off anything that's plugged into these outlets through your computer. It could be lights, a fucking machine (or a fucking machine with tazappers attached in my case), or whatever your imagination comes up with.
On the more expensive side is something like the Spank-O-Matic...
http://www.orgasmalley.com/som/som2.htm
Now a dom/top can actually spank their sub/bottom via the sub's PC software. It's rather intricate software that allows the user to control how hard to hit, when, whether to spank once or in burst, etc.
Here's more about the software, with screenshots. This is mostly meant for self-play and allows users to set all sorts of variables (min, max, duration, random, etc.) for their spanking session.
Taking the above a step further, I also purchased the time-release restraint system that is controlled right through the spanking software. So, I can choose to restrain myself on a timer (alway with backup.. always...) or a dom could also restrain me to the point where I'm fully reliant on them for release (always with a backup, even if it's not for 8+ hours.)
http://www.orgasmalley.com/som/trrs.htm