I'm guessing it's not too high of a voltage since the 7721 is for some highly precise amplification, but I don't think it would be too much of a stretch to add on a 2nd op-amp stage to the output and use that to drive an LED or something similarly low voltage - that way you could see the LED pulse when you have detection spikes.
Would wrapping the open space between the cans aid in improving shielding as well?
Would wrapping the open space between the cans aid in improving shielding as well?