So best strategy here is to make a full-feature desktop client separately from mobile applications. The questions here are that what kind of functionality do you expect for a mobile application ? send/ receive NEM; send/ receive messages what else ?
As others have mentioned, I think it needs to be as simple and clean as possible. I would be completely happy with a first generation app that only sent/recieved NEM, sent/recieved messages, and had a price chart. The key is to make it look good, work fast, and be cool. This app should be free. Ideally, I would guess the mobile app should be designed towards the first time user of cryptocurrencies. I would contribute towards a bounty too. That is how much I believe in this concept.
Later on, a more full featured app that has many more options can be built on top of it.