One LA based company finds a really different niche market - inmates - the people who are in jail. I m sure this is a really interesting niche market. According to the AP report

Finding it hard to express just the right sentiment to your loved one in prison? A Los Angeles company may have the answer. Attorney Terrye L. Cheathem noticed a market Hallmark wasn’t serving and founded Three Squares Greetings, which provides cards for inmates.

“With more than 2.5 million people incarcerated in the Unites States today, I saw that there was a tremendous need,” she said.

I must say this is a niche market that I would have never thought of.