DIY grove modules?

What is needed to make your own grove module? Is it just the grove connectors? Can I use a standard ultrasonic distance sensor arduino module and just use a grove to pin header cable?
Does it need voltage shifting or UART or anything?

The grove modules are so expensive… $20 for a part I can get for $2
I want to use 4 of them with the grove extension header but not if it’s $80.

It works in some kind of modules like Electromagnet, PIR. But it might not work with ultrasonic, since seeed modifies the communication protocol of it. We have tested it before. There is also another way to make third party modules compatible, modify the firmware by arduino IDE and you could find the source code in the github.

Looks like ultrasonic is already standard arduino? The rest have grove libraries though