That would work-except mounting strap for the receptacle is typically connected to the receptacle ground so the cap would be shorted out and ineffective.
Indeed it is... I remembered that last night after the lights were out but just before my head hit my pillow. I did not get up again last night.
My smart GFCI outlet proto is mounted into a plastic junction box but that's probably not to code either.
It would almost have to be a custom built GFCI receptacle (an isolated ground GFCI !)-and that would have to be UL listed to meet Code-and as you pointed out the market probably would not justify the investment.
I think there may be exceptions for use with a non-bonded ground as long as the status or non-status of the ground is labelled.
Not trying argue-just trying to make sure people think through possibilities. In another thread, someone asked about tying the grounds on a couple of Furman's together that were fed by 2 separate power sources. Fed from 2 separate GFCI/stingers would place 2 caps in parallel thus doubling the potential current. GFCI's should still protect-but now this does mandate that all potential sources be GFCI protected.
We can think this to death... The stinger cap current is just enough to trip the GFCI (around 7mA IIRC) so two or three in parallel are still not deadly. It takes some tens of mA to get stuck to the current.
Another concern is stinger mixed with a non-stinger outlet used on say guitar pedals, where the stinger cap is now shorted out and the musician is at risk again. The good news is that my tester tells me the stinger cap prevents ground loop hum should that dual ground path scenario occur, but the guitar player is not protected from external mains faults (like RPBG at FOH or RPBG on the second outlet).
It is usually relatively easy to get things to work correctly as intended-not always so easy to anticipate all the incorrect ways something might be used-which I am sure you understand after a career in design.
Yup... while we can debate how easy it is to get a hum free guitar rig, and how much of a risk this (hot mic) is. But I do not debate that people are remarkably creative about operating things wrong.
I believe that the stinger equipped GFCI power strip is about as harmless to human safety as I can imagine.
#1 if the guitar amp goes rouge and dumps current to it's chassis, it will trip the GFCI removing power.
#2 if the FOH has a hot ground, or if the outlet is wired RPBG the hazard will be current limited to 7 mA.
Lifting the guitar amp ground (as many musicians still do) will actually be less dangerous for RPBG situations, while providing zero protection agains internal amp faults.
Only my smart outlet lifts ground and releases power if it detects excessive current in the ground. This is too complicated and expensive to be commercial. and UL will have an even harder time blessing a safety ground path that goes through a normally open relay.
I am addressing a fairly narrow type of fault. Musicians are more likely to expose themselves to multiple different branch circuit grounds than normal consumers. This is probably rare enough that UL wouldn't want to make special rules.
FWIW I also like the idea of using wireless mics for guitar players (and baptismal clergy, and swimming pool karaoke, and etc). A far cheaper solution to mic shock hazard would be an insulated outer covering for mics. A dynamic mic could even use a stinger cap ground, but phantom powered mics would not be happy.
Note: I have seen a special line cord/plug set that senses current in a ground shield and open up power if a threshold current is exceeded. A variant on this for a GFCI power strip might work and already be listed. (I'll check that out).
JR
[edit] OK ignore that protected line cord...it senses for current shield to neutral, so ground is either pass through or missing... not much help there. [/edit]