I had an large excess of DPDT signal relays, so decided to make a scanning card for meters.
The idea is pretty straight forward, it's USB connected as a virtual comm port, you just send it which channel to connect and it disconnects, delays, then connects the required channel. Then the PC is used to interface with the meter directly and capture the reading.
It has quite a bit of left over GPIO, which my plan is to interface to my HP 3456a GPIB port and trigger in to automate measurements with that meter.
Everything is on Github along with a couple of example Python scripts for using it with a Agilent U124x meter.
I've got most of the parts, boards and relays to build quite a few of these so I may end up offering then for roughly cost of parts if anyone is interested.
Edit: Forgot the github link
https://github.com/harvie256/DMMSwitchBoard