I have a battery-powered product with an ON/OFF switch with two leads. I am looking for a circuit to shine a LED for a short duration each time the switch goes from OFF to ON. Power consumption and cost are of great importance, so any leakage current or similar has to be absolutely minimal; 0.1 μA is too much. The LED pulse needs to be big enough to be noticeable when looking directly at it. The device does not turn on and off often.
I was thinking about charging a capacitor when the switch is open and then dumping that energy through the LED (plus disconnecting the cap) when the switch is closed. What would that look like? What about considerations for leakage? Other ideas are welcome too!