What kind of device would you like to be added :
Koogeek Plugs (P1EU) and Door/Window senors (PDW1)
What kind of category signal would the app use :
- IP (Local/Cloud),
Wifi, app? I think this one is difficult. No API or anything? It’s nowhere yet (Home Assistant or Homebridge)
Is there a (public) API / documentation or known other implementations (like Blogs/Github etc)
I am afraid not, but we do have peer pressure 
Ask for it: support@koogeek.com
Are you willing to loan or donate a device or money to a developer?
Maybe, just ask.