Way overkill, but useable.
You only want to switch low power (current) signals - probably uA (micro-Amps) else mA. 30A contacts are for lights etc.
I was thinking more like this:
... which is a 1A DPDT from Jaycar (see Jaycar catNo: SY4061; 12V DPDT Mini PCB Relay (AUD$4.95) or the similar 5A PCB mounting Jaycar catNo: SY4052; 12V DPDT Special PC Mount Relay ($8.95).
But those relays are fairly common from electronics etc shops & sites. EG - Try searching "FRS6-1 relay" for the first one.
Relays are rated by their coil voltage (eg, 12V) and their contact rating (eg, 30A). As I wrote earlier, don't confuse the 2 specs.
As it happens, your linked relay has contacts also rated for 12VDC (usually they are higher, eg, 30VDC, 125VAC etc).
But its coil current is only 140mA compared to its contacts that can handle up to 30A.
(Coil current deduced from its coil voltage & resistance & Ohm's Law V=IR, hence I = V/R = 12V/86Ohms = .14A = 140mA. IE - Those contacts can carry 215 times the current that the coil uses. [Remember: "amplifier" - not that it amplifies, it merely allows larger currents to be switched.])
And the contacts are like a switch.
Just because a switch can handle 10A does not mean it MUST switch 10A, it just means "up to" 10A.