By now you've seen the various blogs and news coverage of Google Voice for Mobile, the mobile app that lets users make Google Voice calls and send SMS messages from their BlackBerry and Android smartphones. Get the app here.

Google Voice calls to friends, family and colleagues will now appear on caller ID with your Google Voice number instead of the underlying phone number associated with your mobile phone. Previously, you had to dial your own Google Voice number from your cell phone or use the Quick Call button online.

This points to the ongoing synchronization Google is enabling for its applications across all devices. Google consistently and persistently avoids device discrimination.

What works well for our desktops and laptops must work just as well for our mobile phones -- and vice versa. The philosophy is incredibly empowering. I discussed it more here in this post last week.

What I found interesting was how Google Mobile Engineering Manager David Singleton and Product Manager Marcus Foster came to the idea. According to Foster:

David and I were inspired to build this app when we went skiing for a weekend in Tahoe. Like all good Google Mobile team members, we each had three or four phones with us. Of course, carrying three phones while skiing is pretty tough, so we both decided to take a different phone to the slopes each day to see which one worked best as a 'winter sport device'.

Normally, this would have been a nightmare because our friends wouldn't know which number they could reach us on. But since we use Google Voice, one number rings all of our phones. As we were skiing and sending pics to our friends, we had a thought - it's great that our friends and family only need to use one number to reach us. But it's weird that our outbound calls and messages are shown as coming from the phone's underlying number, rather than from the Google Voice number that they're used to, causing confusion.

That's quite the extreme and dramatic way to discover a problem that should have been pretty obvious, no? The whole thrust of Google Voice is to have one number for all phones: home, office and mobile.

Wouldn't that mean you'd have to consider both incoming and outcoming calls to make that one-number-for-all claim? Perhaps I'm being picky, so I'll stop there.

One thing that will have to change is that the Google Voice for Mobile app must be ported for iPhones. With more than 35 million iPhone users and counting, it's a mistake to leave out that device.

Google has been porting its search, Maps and other Web services for the iPhone (and all mobile devices, really), so expect iPhone support soon.