I've mentioned these a couple of times in passing but thought I'd actually make a post about them as I've been using mine for a while now.
http://www.usbbutton.com/
I stumbled across this website, and the products in question, while looking around for a good option to use for a countermeasures "slap switch" for when the hornet comes along. The idea being I wanted to have a button next to my throttle that I could simply "hit" when I have an incoming SAM/AAM and activate the preset emergency CM program.
So using a simple keyboard combination wasn't going to cut it, and I didn't want to bind the command(s) to the HOTAS either given that's not where it is in reality.
I purchased one of the buttons a few months ago and have been using it (reasonably lightly due to my current situation) for a while now. The functionality is pretty simple, it's a button that connects via USB and can be programmed with the accompanying software to send a key combination or preset command (such as opening a website). Once programmed the settings are stored in the button itself so there's no need to run any software in order to use it.
I found it to be very effective, the only issue I've had is that DCS doesn't seem to like commands where modifiers are used (eg shift + key) although the button is sending them to the system as intended. I need to do a bit more fiddling there to see what needs to be done.
I got myself a second button last week and have that set up to use as an emergency jettison switch (another button you don't want to have to think about how to activate or fumble around with the mouse).
I've set them up as below, left had side is for CMS and right is for emerg jett. Both just fixed with sticky pads.
If anyone is looking for a similar solution at any point I'd recommend giving them a try.