I'm doing a series of articles on WonderSwan cancelled games. The most curious (well along the pocket sonar) add on I've seen for WonderSwan (and even in general) was this balance board made by Tanita that can comunicate with Bandai's WonderSwan. The aim of WonderSwan Mama Mitte was to help women along with the pregnancy process. Look at the following images:
interesting. The sonar you talk about is the one for fishermans right? i thought it was released back then.
The sonar was released, this thing too (I'm not 100% sure). The Mama Mitte or Handy Sonar has nothing to do with the "cancelled stuff" a briefly talked. I just though they were bizarre and obscure.
