Ok, so the zoning panel (Honeywell) is right next to the air handler in the basement.  I can't tell upstairs on the main floor if stage 1 compressor, stage 2 compressor, or aux heat is on.  I can tell aux by the t-stat, although in another post about 2 stage resistive heat, I ponder how both stages are controlled and how one can monitor them.

My goal here is to be able to tell, from upstairs at a glance, what's on.   Example:
Green LED 1 - compressor 1
Green LED 2 - compressor stage 2
Red LED 1 - stage 1 resistive (10 kw)
Red LED 2 - stage 2 resistive (another 4.4 kw, for a total of 14.4 kw)

Would it be possible to put the LEDs across the Y1 and Y2 lines that run from the zoning panel to the heat pump?  Of course, the LEDs would be wired with resistors, maybe a high voltage diode, to help turn the 24 VAC control signals (I'm assuming??) into a reasonable voltage/current.

How would I monitor the resistive stages??  Right now, I have one of those little AC voltage checkers (the ones with the orange neon bulb and 2 little probes)...I bent the pins on the ends of the probes and (with the breakers off!) connected the probes across the resistive heat relay (black switched wire) and white.  The voltage checker is rated to several hundred VAC, and the resistive heat is 240 VAC.  Then I shoved the neon end of the checker out one of the holes in the case that holds the relays, so at a glance in the basement, I can tell if aux heat stage 1 is on. 

Is there a way I can (on the cheap) bring that "signal" upstairs to an LED?

Could I put a photocoupler and a couple transistors and attach it to the neon bulb end of the checker?  I DON'T want to tap directly into the 240 volt circuits, and I'm a little nervous leaving the voltage checker "permanently wired".

I see on the relay board a control wire from the heat pump with a V+ and 2 V-, and the schematic says that one of the V- controls stage 1 resistive and the other V- controls stage 2 resistive....I'm assuming these are 24 VAC control lines, and that I could tap THOSE for stage 1/2 resistive monitoring??

I'm trying to not spend several hundred on a WEL server at this point.

Meanwhile, the DATS (Duct Air Temp) read-out is on the zoning control panel, UNDER the plastic cover for some reason.  So I wired an external temperature sensor into 2 lines of the thermostat wire that aren't being use, put the sensor in the basement IN the supply duct right by heat pump, then upstairs connected the 2 lines of thermo wire to S1 and S2 (the "outdoor" sensor connection) of the thermostat.  Then on the thermo, programmed it to just read the "outside" temperature.... the result, I have a DATs readout right on my main thermostat!  Air is currently 97 F :-)

Sorry, I meant, Y1 and common, and Y2 and common. I guess I wanted to put very small LEDs with minimal current drain in a little panel next to the thermostat. Rather than have multiple 24 VAC lines running to bulbs, I figured LEDs. If small bulbs in red and green (grain of wheat sized) are available in 24 V combinations with minimal current drain, I could certainly use those, too.

Screw the blinkly light thing, for what the system cost, I want a full color LCD screen with some nifty graphics and a full diagnose readout of system status.

For a bit over $30 each you could buy and connect four Readington LCD hourmeters. They increment hours and tenths based on presence of any signal voltage between about 20 and 277. They blink their decimal point when timing.

With such an install you'd have data telling you not just what is on but how long it has been on - much more useful in estimating total costs.

If you are bound and determined to stick with an indicating light solution, there are probably ways to configure LEDs, resistors and a square wave rectifying arrangement of a quartet of diodes. I'd suggest experimenting using an irrigation 24 VAC power supply (~$10 at HoDepot) so as to avoid releasing factory smoke from control power circuit.

A KISS solution could be had with very small 12 volt bulbs common to cars and boats. Wire two in series for each 24 volt signal you wish to monitor.

IMO by the time you chase down and implement all the details of a light-annunciated solution you could be into it as much as for the Readingtons, but with far less useful data.