Hi mr snyper and trickrick. This is my first time posting, so I hope I am doing everything right.
I too am working on a DIY e-caller and ran across this forum. What you are talking about doing should be pretty simple. I made a diagram that should work for what you were talking about.
I would recommend using a 9.6v rechargeable battery, like the type used on most RC cars. Cut the outside of your housing so that the charging plug, located on the battery, would fit where you would be able to plug the charger into it. Inside of your housing, tap into the positive and negative wires on the battery.
Run the negative tapped wire to the LED and the amplifier. Run the positive tapped wire straight to the switch. From the switch, run the positive wire to the LED and then, from another tap, to the amplifier.
This type of wiring should allow you to be able to charge the battery without removing it from the housing. Any other battery with a charger would work as well, but this type should work well and last a long time on a charge.
I would be careful if you did wire it like this and make sure that the switch is turned to the OFF position when charging. The chargers for those batteries put off 12-14v, which could damage the amplifier and the LED - but it could also work fine and not damage it. I don't know a lot about circuits, so I can't be sure what would happen.
