Is there a way to create a new player control, i.e. how can I assign a key stroke to perform my new action?

SCript Extender, if it supports it yet.

Oh, I was hoping it would be simpler. I wanted to be able to press a button to run some script.

I guess a way round it could be to have an equippable item as one of the hotkeys that, when equipped, remembers the item that may have been unequipped in the process, runs the script, then unequips itself and re-equips the other item.

You'll want Skyrim Script Extender then.

Bool bIsHotkeyPressedInt iHotkey = [DXScanCode of your choice here]Event OnInit()	RegisterForUpdate(0.2)EndEventEvent OnUpdate()	If bIsHotkeyPressed != Input.IsHeyPressed(iHotkey)		bIsHotkeyPressed = !bIsHotkeyPressed		If bIsHotkeyPressed			; Do Something		EndIf	EndIfEndEvent

Thanks for that.

If I make a mod using the script extender, will anyone who tries to use it need to install SKSE as well?

Yes they do.
It will be much beneficial in the long run, as in Oblivion, best mods were made using OBSE (Oblivion Script Extender). same goes for Fallout3 , Vegas, etc...

Indeed. The Script Extender wasn't a big deal for Oblivion, Fallout or New Vegas, and it won't be a big deal for Skyrim.