Musical Wedding Box

Some good friends of mine got married last year and instead of gifts, they collected donations for charity.
The groom asked if I could rig up a treasure box to play music whenever it was opened. This seemed like an interesting task so of course I said yes.
He found a really nice timber box and I started hacking. Being such a nice box, I didnt want to make any permanent changes, so i built a false wall in one side.

I mounted some neodymium magnets into my false wall and added some small screws into the side of the box, now the false wall is removable and is held in place with magnets.
On the back of the wall, I installed a cheap mp3 player module from dx.com, the amplifier and speaker from a promo phone speaker i got from somewhere, and single cell from a 2200mah lipo that had a dodgy cell.

To trigger the circuit, I pulled the reed switch from a door sensor and mounted it in a hole drilled in the top of the false wall, the switch is held NO by another magnet held in the lid. When opened, the mp3 player powers up, and automatically plays a song from a microsd card.