[AlexeyBrin]

If you know and enjoy coding in Ruby, you intend to target only iOS, and you don't know Objective-C, C or C++ than RubyMotion is a good investment.

On the other hand, if you want to target iOS and Android you'd better learn Objective-C and Java. An interesting alternative is to use HTML5 and JavaScript if you already have a good background as a web developer.

[gebe]

Or, if we disregard costs, C# and use Xamarin's (http://xamarin.com/) products.

[AlexeyBrin]

Same goes for C# and Xamarin, if you already know C# and enjoy coding in C# ...

If you don't know C# I see little reason to buy a Xamarin license (I know you can get started for free which is great).

[gebe]

Code sharing between platforms could make it a worthwhile investment of time and money. But it's quite costly if you are just starting out.

[evilduck]

http://ruboto.org/ also exists, so you can stay in Ruby if you like.

[adamors]

This looks really cool, curious if anyone uses this in production.