Remove Unknown Device from Gateway

My gateway shows a device connected and I can't figure out what it is. 

Device name is: Shenzhen iComm Semiconductor CO. LTD

Websearch indicates it could by a spy cam or listening device. Recently went through a breakup. My ex was making comments about how he could give me exact dates & times of speakerphone conversations I had in my bedroom.

I have searched everywhere in the room, disabled the device on my wifi, changed router admin & wifi passwords, but the app doesn't give me an option to remove the unknown device completely. How do I remove it from my network?