I've been making apps since 2009. I'm fluent in all the latest technologies for both Android and iOS, and I often make Mac apps and write Python server-side code. I spend most of my time developing in these technologies for startups, and the rest of my time working on my own projects. I've also been consulting with startups, helping them decide how to go about building an MVP and what should go into it.
For consultation, my rate is £150/hour. I'll work with your team to plan, architect and review how to build your mobile application. I've made enough apps to know where the foreseeable problems will arise and where the bottleknecks will be, and will work with you on making sure you avoid as many as possible.
For short term projects, my rate is £550/day (8 hours). I prefer to have people book my time in advance, and the minimum booking period is 5 days. I primarily work remotely, but can arrange to work on-site if it is beneficial. As a rough guideline, a project like Entree should take me about 12 days end-to-end (including testing and integration), whereas a more simple project like Postnote would take approximately 5 days.
I prefer not to sign NDAs. If this is a requirement for you, there is a £1000 fee. I will also request you sign my consulting agreement (which includes confidentiality clauses for your benefit).
If you'd like to talk more, email me.