You (supposedly, I haven't looked into it) can develop for iOS on a windows or linux machine. (I believe the Unreal dev kit works like that - you must develop from a windows machine.) If you're willing to figure out how to do that, I'd suggest an iphone.

If you're set on android, then my recommendation is to get a Nexus.

While it's probably possible, it's far from ideal. You'd certainly have to put in more effort, and you'd likely end up with an inferior product.

I am a diehard Apple fan, but in this case I have to recommend a nexus.

I also think it is far from ideal and I permanently switched into Linux, want to stay and develop on Linux.

If I do a contract for 24 months, I will pay 99$ for Galaxy 2, and 49$ for Note, and 599$ for Nexus. Do you think it is worth of this much difference?

The Nexus is 599 with a 24 month contract? That is definitely not worth it. The Galaxy II is supposed to get the 4.0 upgrade, the not will most likely get it as well. I'd say if you don't want a gigantic phone, go with the $99 Galaxy 2. If you want a phone so large that it doubles as a tablet, go for the Note. If it is $599, I wouldn't recommend the Galaxy Nexus unless it is off contract.

I totally agree on you. I have some concerns about the update issue so for resolution, I am planning to wait the start of January. Today, there was news about update is very likely. If it is the case, I will go for Galaxy II. Moreover, I have already asked Nexus, it wasn't on the stock now.

What about a refurbished macbook and iphone, or ipod touch and dumbphone?

Thanks for suggestion but I have a pretty good machine and don't think changing it in a very short time.

I understand that you like your computer, but you should determine what platform you want to develop for, and then make your decision based on that. If you want to develop for the iPhone, having a cheap second computer is a viable option.

I'm deeply in love with my Samsung Focus, which runs WP7.

My operator(Orange) doesn't present this option.

I think Orange offers the Nokia Lumia 800. It might be worth a try.

Yes, Orange offers Lumia 800 but it is in pre-order and since I have money, I want to buy the phone as soon as possible.