This Medium post from 2014 by Chris DeSalvo makes for fascinating reading, as it documents the early days of Danger, the company behind the Hiptop line of mobile communicators, which are probably better known by the name Sidekick given to them by T-Mobile in the USA.
In many ways, the Hiptop / Sidekick was far ahead of its time, with features that we now take for granted on iOS and Android devices. And they turned out to be a godsend for deaf users. Sadly, I don’t think they ever caught on outside of the USA, which would explain why I’d never really heard of them or known of their existence.
I found this article via a recent video from Michael Fisher (aka MrMobile), who has started a series titled When Phones Were Fun where he shows off some of the more interesting / oddball phone designs from years gone by.