To begin with, I wrote the code contained in the gist here https://gist.github.com/gomako/4bcd3731af11896e7985f0d88a0af0a5 and made it flash the in built LED on and off on the Espruino (https://www.espruino.com/Pico) board. I've tried to comment the code as thoroughly as possible, and essentially this is what happens:

1. Connect to WiFi
2. Set the UTC time on the Espruino
3. Connect to the http://open-notify.org API using the location you set, this returns the next five passes in your area
4. Wait until the next pass happens
5. Flash the LED for the duration of the pass
6. Repeat!

Then I tried to figure out how I was going to build the thing. I decided on getting some passthrough female headers like these https://www.jameco.com/z/A000040-Arduino-Stackable-Female-Headers-for-Arduino-Shields-1x8-and-1x6-Position-2-each-_2137756.html so that I could bend the legs and make the thing stand up nicely, and also be able to solder on the 0.8mm brass rods (you can find these on ebay).

I soldered three lengths of brass rod to a Neopixel and connected them to VCC, Ground and pin B5 on the Espruino. To make it look more spacey, like a satellite I soldered on a couple of small solar panels that I had in my junk box. I also added a micro USB breakout and anchored it in place with lashings of hot glue.

Then you upload the code, turn it on and that's it! It flashes away when the ISS is overhead!

I did make a version where I attached a servo and had it actually wave, but it was very noisy and woke me up in the night, so I got rid of it, and LEDs are prettier anyway.

I like using the Espruino as you can connect and hack about on the fly, instead of the code, upload, serial monitor, fix bugs etc flow of Arduino.