Third Party Dreamcast Jump Packs
From Sega Retro
The Sega Dreamcast was the last mainstream video game console to have detachable rumble/vibration (or in the Dreamcast's case, "jump") packs to help immerse the player within the game. The official Dreamcast Jump Pack was often seen as expensive, bulky and heavy, so several third party manufacturers produced their own. Also unlike the VMU, Sega only produced one the Jump Pack in one colour - white.
There are some interesting third party variants of the Jump Pack. For example, Joytech's "Advanced Jolt Pack" contains 128kB of memory, meaning it doubles up as a memory card. Mad Catz's "Force Pack" has an LED which flickers when vibrating.
This page lists all of the third party jump packs we know about. It is likely incomplete.