I agree with AbenezerMamo that you should build something new with some hot hyped tech as opposed to a side project with revenue generation goals. It is very ha

I agree with AbenezerMamo that you should build something new with some hot hyped tech as opposed to a side project with revenue generation goals. It is very hard to generate revenue that fast, stay where your expertise is. Build something that will work as a portfolio for your agency, a showcase of your skills. That's why I think it must use some new hyped tech. You want to build something that the press will pick up. PR is much easier when you are building something free, cool and using a new tech. With 4 iOS people, I would definitely choose to build something using Apple ARKit. It is among the most hyped things right now, everybody that tries it loves it and it still with very little reach, meaning there are not many products out there using it. If you build something really cool using it you can get enough attention from the press and fill your pipeline with prospects to build something with ARKit (doesn't matter if in 5 years AR will be the new forgotten tech like Google Glass, until then, big companies will be investing a lot in it, just in case). That way you keep making your business stronger, not starting another one from scratch.