The first question to answer when discussion a mobile app is - do you really need a mobile app or will a mobile optimized web application meet your needs?
Libraries like Bootstrap make it relatively easy to optimize your web application for mobile.
In addition to writing the code, you need to get the app published in the Apple App Store and the Google Play Store. Technicality maintains active accounts in both the Apple and Android developer programs and has successfully published apps to both.
If you'd like to talk about developing for mobile, click here to schedule an initial consultation.