Dear ricardonacif,
don't be mistaken by my missing reviews here - I'm freelancer beginner, but I'm skilled developer. I have been in professional programming industry for 10 years (as a R&D and teamleader), within school and programming for fun much longer. Last three years I'm working mainly on Android and I was developing for Android even before first hardware device existed. I can assure you that if you work with me once, you will always want to work with me :).
I'm unable to ask questions here, so I'd like to know - with Facebook login you mean 2FA? Something like "user can login on his phone to facebook and then authenticate with that information to your server"? If so - I did 2FA before - for Yahoo servers, but it's the same.
Also I'd like to ask - are you planning to optimize just for phones, or tablets too? Which android version?
If you'd like to, we can Skype about details. Within week we're good to create very good application, trust me - I've been to some hackathons and we did cool stuff within one weekend ;).
Looking forward our cooperation
Vaclav