Ask HK: What about niche market software startups

It seems that most information out there are about public facing product, by that i mean startup companies which have their main product geared toward the general public ( Yelp,facebook,Airbnb etc...). I am wondering what is it like for companies with a specific/ constraints demographics, like security system for stores, Financial application for trading firm,medical/research/weather forcast. applications etc... Are those market amendable to startups ? Does targeting those market change something significant (like more focus on revenue instead of share value) Anybody with experience in this care to share his/her point of view.