Back in the '60s, the Sunn portable AFR meters had a sniffer tube that was placed in the end of the exhaust pipe (careful not to scoop up any of the lead deposits in the process AND had to ensure the engine was warmed up so no condensate was in the pipe). Not much lag time between the idle adjustment and when the meter changed, as I recall. That was on our '66 Newport 383 2bbl. The idle could be adjusted to the 14.2 spec, although it was not a CAP car. Taking the rpm up to 2000 or so, in "P", would yield 14.7.
The orig O2 sensors were not heated. The "heat" was needed to get the sensor up to temp sooner for closed-loop cold start emissions. The faster the sensor heated, the sooner the computer could go into closed loop. Which turbo cars needed more than the earlier carb/efi cars did, but ALL cars needed them later-on. The turbos acted like a huge heat sink for the exhaust temp during a cold start (cast iron cylinder heads and exhaust manifolds could probably be in that same "heat sink" category, too?), so the much more expensive heated sensors were needed to make things work as they needed to.
The new clamp-on bungs look pretty easy to do. Possibly replace it with a modern exhaust clamp that is a full-circle tubular design, after the tuning is done.
ColorTune was an interesting concept, but I recall thinking that you'd need to have several of them to ensure that intake manifold a/f distribution was not a factor. Like adjusting a Dearborn gas heater, you'd have to match the colors seen to what it needed to be?
I like the idea of a phone app display, especially if you could Bluetooth it.
Just some thoughts,
CBODY67