[bsder]

One caution about folks thinking about foot pedals: your operating system might get in the way.

OS X, for example, can't use the foot pedal for "Shift" and apply it to the "A" that you hit on the keyboard if they are two different USB devices.

So, you may need a keyboard that the foot pedal plugs into in order to avoid this.

[voltaireodactyl]

I can’t be 100% sure, but I’ve been able to solve that problem by using Karabiner and making sure both devices were checked in the preferences of that app.