First of all, you've left out some essential information. You haven't told us what operating voltage range the guage is designed to see. Put another way, your gauge might expect to see a 0 - 1 Volt swing dependent on what the actual air/fuel ratio is. There are two problems with this if that is the case.

The Air/Fuel ratio is typically determined by the oxygen content in your exhaust. It's done with the O2 sensor. You probably have one in your exhaust manifold and one in your catalytic converter. The manifold sensor is the one your ECU uses to calculate your fuel-injection pulse width so thats the one you'd take the reading from. The other is to monitor proper operation of the catalytic converter.

However, there are two or three problems you are likely to run into. The first is that the voltage swing across the O2 sensor may be 1 volt in magnitude but it may be offset by another DC voltage. For example, the swing may be 2.5-3.5 V. This isn't gonna work too well with your gauge without some electronic middemen (maybe a differential amplifier). Also, depending on the construction of the O2 sensor, the ECU may read a current value from the circuit and not a voltage across the sensor. While these two things are related, adding a gauge to the circuit will change the impedance of the system and the readings for the ECU will be corrupted (also potentially solved with some custom eletronics - high impedance amplifier, etc).

If you can get past these first two electronic problems, there is still one big one left. The O2 sensors in the 5th gen accords are not wide-band sensors. I.e. their voltage/A/F ratio curves describe a switch type behavior. They show one signal for rich and another for lean with no linear middle ground. Your A/F gauge is essentially useless with this in mind because the reading will just oscillate between rich and lean. It might hover on one for a bit if you coast or really get on the throttle. The point is that to make this work, you really need some more sophisticated sensors and eletronics. I know that wide-band O2 sensing kits used by race teams run from 500-10,000 dollars.