Fragmentation and fierce competition are enemies of one size fits all mobile solutions.Mobile is the not-so-new-hotness. There are many, many, many companies and people building products and apps targeting mobile first and mobile only. But there aren't many who are succeeding.The reasons for failure are often simple and obvious and easily avoidable.

Device fragmentation

Pick a device.If you choose the right device for your application, website or product and this device is relevant to your target market then you wont have to support every device under the sun upfront.Test your market with a single device or OS, just make sure you choose it wisely and own it. For example, in Africa, if you can build something for the Nokia S40 devices and it works, you'll do just fine.

Market fragmentation

Pick your market. Be it a country, city, gender, age group, creed, all off the above or none. Just pick one and go after like a you are possessed.

Country

Pick a country. You can't be everything to everyone all the time right off the bat. Conquer a single country and then consider moving on to another.

City

Maybe consider picking a city. Some cities, like Lagos, have nearly 20 million people in them. That's not a bad place to start.

Age

You cannot market a product targeting every age. That's just not realistic. A 13 year old is not looking for the same things as a 60 year old. And don't tell me that if Facebook can do it, so can you. Facebook started with a single age demographic.

Attention Deficit

Users are constantly being nagged for their attention.The product you are nagging me about needs to make me feel like I can't live without it. The applications and products that do this best for me are the ones that do a single thing amazingly well. I don't have a single app that handles photography, social, music, video and everything else all in one. That's called a mobile phone.Your app needs to do one thing and be the absolute best at that one thing to grab (and keep) my attention.

Niche, Niche, Niche

The chances are that your product, app or website is not going to compete with Amazon, Google, Facebook, Twitter, Instagram or even the local equivalents of these behemoths. Something you build may one day grow into a competitor to these players but they all started in a niche; search, photography, university.Pick your niche and go after it like there's no tomorrow for your company. Don't let anything stand in your way. Own that niche, make it yours and dig a moat that prevents anyone else from owning it. Then expand that niche little by little. This is how you build a sustainable business.