Unless all you want to do is track where your friends are all the time--which sounds sort of creepy, if you ask me--you'll probably spend a lot of time using Latitude's mobile interface. The interface varies a bit, depending on the device you're using it on, but this walkthrough of the screens on my BlackBerry Curve will give you a good sense of what it's like.
Google Mobile & Maps
On the BlackBerry, Latitude lives in the Google Mobile App, which you can download by browsing to www.google.com/mobile on you device. Even if you already have Google Mobile and Google Maps on your BlackBerry, you must download the latest version to get the Latitude features.
In Google Mobile, select Maps from the menu. If you have an older version of Maps on your phone, you'll be prompted to download an update now.
Initially, Latitude won't be enabled on your phone. Hit your menu button and then select Latitude to enable it. You'll need to enter your Google account user name and password, but afterward you'll have access to the features I discussed earlier in the Web interface section.
Mobile Friends List
The Friends list in the mobile version is just like the Friends list on the Web, except that it's slightly truncated because of the smaller screen. Instead of sitting off to the left of the map window, it hovers over the map, so you can't see what everyone's doing while you're looking at their position.
To add a new friend, click Press menu to add friends at the top of the Friends menu; you'll be taken to a screen that gives you access to all of the same contact list options that you had on the Web, including the option to enter new addresses manually. The Most Contacted option is quite helpful in this context, because it saves you from having to scroll through the names of hundreds of people you don't want to track or share your location with.
To customize the options for a given friend, highlight the person's name in the Friends list, and then press Enter to bring up the person's Options menu. Here you can get directions to the friend's current location (which could be unhelpful in light of possible spoofing), search for things near that location, adjust the level of sharing you'd like to enable for the friend, or dump the person from your Latitude tracking group.
Satellite and Traffic Views
Because it's built on Google Maps, Latitude has all of the same traffic reporting and satellite views you're accustomed to working with on your phone. Simply enable these options in your menu to see the corresponding details on your maps.
The Traffic view is especially cool when you want to see whether a friend you've arranged to meet will be on time. Just look for any red lines between that person's location and yours; such lines signify traffic delays. If the roads are all green, the friend will have no excuse for being tardy.
Quirks and Issues
Latitude is a brand-new service, and it's not without issues. But it's difficult for me to tell how many of these issues are the software's fault and how many are the result of the phone's underpowered GPS hardware. Mobile phones have long suffered from inaccurate GPS readings, resulting in all kinds of headaches with turn-by-turn directions and other basic location features.
It's not surprising, then, that Latitude often reports strange and inconsistent locations for its users. In my case, it generally showed my friends that I was several blocks--and sometimes several miles--from my actual position. Furthermore, it often bounced me around from one second to the next, showing me at my house one second, five blocks east the next, and then in a field a mile to the west a few seconds after that.
So while Latitude is an impressive little tool for keeping in touch with your friends, coworkers, and employees in real time, it's not exactly reliable if you're hoping to track them down to within a city block. Of course, anyone who is worried about privacy probably won't mind these little discrepancies at all.