Yes, electric paint. And yes, it's nontoxic, solvent free and water soluble. And yes yes, we admit we're a bit head-over-heels for the stuff.
You, your child (or your inner-child) can use it to draw circuits, solder components even do repairs. The pen creates a "liquid wire" that will conduct electricity from your power source to a circuit. It works on traditional electronics, plastic, paper, cardboard even textiles and is compatible with conductive thread, PCBs, microcontrollers such as Arduino, Raspberry Pi and FLORA.
To use, unscrew the lid and nib and remove plug. Gently squeeze the pen to apply the liquid. The paint dries at room temperature in about 5 minutes and becomes conductive once fully dry. It comes off with soap and water.
Bare Conductive have a fantastic website full of ideas and tutorials. We highly recommend it.