The idea behind the light bottle is to have something similar to a small diffused plastic bottle which will have a few RGB lights inside and a controller to play with colors or receive your commands over Bluetooth.
Any suitable plastic bottle. Preferrable with diffused semi-transparent plastic
Arduino Pro Mini (ATMega328)
Or any similar controller be able to drive WS2811/WS2812
Chainable and individually adressable RGB LED
Li-Ion Charger / Step Up converter
5v - 3.7v converter and charger for Li-Ion battery
I tried to experiment with AA battery instead of 18650 Li-Ion. The design is slightly smaller and lighter, but I think it will be worse on the long run. 18650 can provide more power and it's easier to have step up and charger on the same board.
I recycle my 18650 cells from old Laptop batteries. Usually those batteries go bad just because of 1 or 2 cells only, while other cells are still usable.
Or you can always buy 18650 cells online if you don't feel like cracking up laptop battery or don't have one to spare.
My rough estimates are about 150mA while light bottle is on, so 18650 should be plenty for several hours of your night talks.
I just completed with the initial concept in hardware using 4 WS2812B LEDs. I still need to figure out the easiest way to turn on and turn off the power. There are a few tricks I want to try -- controlling it with some mosfet and be able to turn on with a light tap, and other similar ideas.