What does "replacing" have to do with anything? You said it was not useful in real world applications. It's quite useful.
Cellphones are niche applications??
What millennium are you in?
There are more than 4 billion cellphones in the world. That's better than 1 in 2.
10 year olds
have cellphones. 10 year olds don't even have cars. Are cars a niche application?