I've decided not to get huffy and private about my good ideas, or worry about people stealing them. It's unlikely someone's going to steal my idea unless they get as excited about it as I am, and I'd prefer the additional motivation I'd get from hearing feedback and suggestions.

So here's some of the Android app ideas I've had lately, and would like to set some time aside to work on. Let me know what you think.

An "achievements" system, in the style of PS3 trophies and Xbox achievements, with a broad range of possible awards. There could be achievements for talking for insane amounts, or getting late night calls from women -- or since the thing's got GPS, it could reward you for flying frequently, or spending a night in jail, all sorts of things. This would definitely require a web-based service backing it, with a UI, and preferably some community elements, so it's a huge undertaking. But potentially completely awesome.

A minute usage tracker. Specifically, I'd like to downgrade my voice plan from 1000 to 400 minutes, to make up for the cost of my new data plan. But I'm terrible at remembering to wait until 9pm, and I'd also like to know if, on the 10th of the month, I've used more than 1/3 of my monthly minutes. So this would watch your minute usage (and if you have a nights/weekends-sensitive plan, then just daytime minutes), and let you know if you start endangering yourself. One idea: if you initiate a call between 8 and 9pm, it will make you go through a screen acknowledging that you could just wait until 9pm and save yourself some money. Doesn't need any other system backing it.

In a similar vein, a financial tracker. So, I'd say that I want to spend only $30/week on eating out, or $100/month on entertainment, and this could use, for example, the Wesabe API to track my expenses and let me know if I'm going off course. I'd enjoy notifications at night if I did an especially good or bad job, and a message in the morning letting me know how much I should spend that day to stay on course. In other words, it should be proactive, and reward me for good behavior without me having to ask it. Like many people, I can go a while avoiding looking at bills and money if I'm afraid of what I'll see, so a service like this would help a lot. This wouldn't necessarily need a web-based system backing it, but it could give a better UI, and you could let people sign up to have these messages come through just SMS. So this isn't just Android-specific.

All right, well those are my three for right now. I should note that none of those could be done right on the iPhone, for as long as Apple doesn't let you run apps in the background. Android also lets you do awesome things like intercept incoming and outgoing calls, something I can't see Apple ever allowing -- so subtle attempts at guiding behavior, like warning you before you make a potentially expensive call, are only possible on Android.