Optional, but HIGHLY suggested when using expression recreation: A Tensor Processing Unit (or something that can serve as one, a GPU on the SBC will work, otherwise refer to Taurus' TPU support).
Optional, but suggested: Bluetooth Module (as long as the SBC has one and the OS has drivers for it, you'll be fine)
Optional, but suggested: WLAN module (same as above, Hub uses the OS's IP stack)
Body-safe Battery
Reboot/Fitz mainly uses a belt-mounted LiPo battery pack (see: CORE's modules), but you can use just about anything that'll: