I got that new battery tester today and I modded my Tx out.
I ended up wiring it rather unusually. With the voltmeter having "in" wires and "out" wires, I was going to straight forward connect the "in" wires to the battery and the "out" wires to the Tx, but then I'd have to disconnect it after every use. I tried wiring the "in" wires in series with the Tx power input, but then it would show the volts at 8 instead of 12.3; Which isn't bad, I could still tell when the battery was getting low.
Anyways, I ended up mounting the battery checker into the Tx. The "out" wires don't go anywhere, and I have two sets of wires for "in" wires. Basically, I have two loose wires sticking out of my Tx so I can plug in any of my batteries to check their voltage and I have a 9volt battery clip that I can plug straight into my Tx battery to check it's voltage. Unusual set up, but this allows me to use my voltage checker on any of my batteries and it's right there inside of my Tx.
I want to point out that the battery checker I bought
http://www.hobbyking.com/hobbyking/...oltage_and_Amperage_Meter_USA_warehouse_.html shows both volts and amps, but it will say "0.0" for the amps. I'm guessing that it keeps track of amps used, it can't tell how many amps are left. This checker is meant to be installed into a plane and used during flight. At only $5.15, I'm tempted to buy a second one and actually use it for it's intended purpose.