USB Arduino device meets Android mobile

Essentiall开发者_如何学JAVAy I'm looking for a project to do, and since I'm biking quite a bit at the moment, I thought I'd build a speedometer that does a lot more than just display the current speed. I realise I can just do this via GPS, there are already people that do it, but from using them I can say that the speed readings are not accurate and not updated often enough for my liking.

The Arduino device would more or less exist solely to read and possibly calculate the speed and maybe some other stuff. I'd love to this over USB, but my searching has revealed that it is most impossible on current phones without rooting them. Fine for me, but if I want to share the project, it limits the people that can try it out.

If I gather correctly I have no choice but to use a Bluetooth module of some sort for the Arduino device so that it can send the data to the phone. Is that correct? I've found quite a few links, feel free to share anything particularly good. Much appreciated.

Sort of unrelated curveball question: Is it possible to build a battery pack that hooks into the micro-USB port to charge the phone using AAA, AA, 9 V, etc.?

If anything here isn't clear, please do say. Just FYI, I am using Gio running (2.3, I think, maybe 2.2).

The Arduino device would more or less exist solely to read and possibly calculate the speed and maybe some other stuff. I'd love to this over USB, but my searching has revealed that it is most impossible on current phones without rooting them. Fine for me, but if I want to share the project, it limits the people tht can try it out.

Android Open Accessory Development Kit, if you're running 2.3.4

Sort of unrelated curveball question: Is it possible to build a battery pack that hooks into the micro-USB port to charge the phone using AAA, AA, 9 V, etc.?

A variant on the MintyBoost. You need a decent current (at least 500 mA) and 5 V.