Microsoft is inviting testers with iOS devices to sign up for an early preview of its "Phoenix" expense-reporting application.

Phoenix is an "experimental" app that's part of Microsoft's Garage incubation program. It's not clear if Phoenix has or may soon move beyond that status to a commercialized Microsoft app.

According to the Facebook page for Phoenix, Microsoft launched a limited beta of Phoenix as of March 18.

Over the past couple of days, the Microsoft Office Pre-Release Programs Team began sending e-mails to both business and consumer customers looking for potential testers.

According to those e-mails, a copy of which I've seen thanks to one of my contacts, the preview participants need to be based in the U.S. only (for now), use an iPhone as their primary mobile device; work at a company that uses Concur as their expense reporting back-end; and who are actively traveling with at least three domestic overnight trips per month. Those hoping to qualify for the beta also need to complete a nomination survey.

According to the Phoenix Facebook page, "the phoenix team began with a simple realization: expense reports suck." Little has been done to improve the expense-reporting process "since the linked corp card was introduced many years ago," the page adds.

More from the team:

"We decided talked with hundreds of account executives, to go deep on this problem, and understand what it's like to be an frequent business traveler today. "We took all of our learnings and created the vision of Phoenix: a mobile app that uses all the smarts we can gather to automatically fill out your expenses for you. Then, by giving you a notification of your credit card spend in real time, we let you glance at at the expense, approve it, and be done forever. "Today, our first cut of Phoenix is alive. It's still early - we've got a way to go to bring this vision to life - but we're now ready for others to join us on our mission to slay the expense report beast!"

Another Web page for the Phoenix beta notes that the expense-reporting app is integrated with contacts mentioned in users' Outlook calendars. It also uses the cameras on mobile phones and a built-in agent to classify entered expenses into the right categories (hotel, taxis, meals, etc.).

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"Phoenix works directly with your expense system, so there's no hassle," according to the beta's feature page (despite the aforementioned specification for Concur on the back end currently).

I've asked Microsoft officials for more about Phoenix -- whether Microsoft considers it just an experimental Garage app or whether it's going to be commercialized and made available for Android phones and Windows Phones, too. No word back so far.

An expense-tracking app like Phoenix would fit in nicely with Microsoft's productivity and platforms vision, as well as its quest to make productivity apps more intelligent.

An aside: Microsoft codename buffs will know that this isn't the first time Microsoft has used the Phoenix codename. There's the (possiblly still active) Phoenix universal compiler team and the Dynamics CRM Parature "Phoenix," as well.