I got a lot of work done during a recent road trip, thanks to my new assistant. As I drove, she added some meetings to my calendar, took an e-mail dictation, and found some restaurant options for dinner. She has a great sense of humor. When I jokingly told her I loved her, she responded, "I bet you say that to all of your Apple products."

As you probably guessed, my new assistant is Siri, the voice-command system built into Apple's iPhone 4S. To see how the feature stacks up against other voice-recognition systems, I compared it with Vlingo, a free app for Android phones, BlackBerrys, and iPhones.

Using Siri is a cinch. Hold the iPhone up to your ear, or press and release the Home button. Then speak your command. Siri takes you through step-by-step directions to complete its assigned tasks. Say "Send a text message to Jim," for example, and it will prompt you to speak the subject line and message, then say "send." During my tests, Siri took dictation for texts and e-mails accurately most of the time but got tripped up by some unusual words and proper names.

You can also use Siri to send reminders to yourself. I asked it to "Remind me to send a message to my editor when I leave work," and a note popped up on my phone when I left the office. I also used it to add meetings to my phone's calendar, play music, check stock quotes, and dial up FaceTime chats.

Siri can search for things on Google, Wikipedia, and Yelp, as well. When I asked it to find an Italian restaurant in Minneapolis, it pulled up a number of options from Yelp, along with a Google map. I asked Siri, "Who is the founder of Zynga?" and it produced Google search results for Mark Pincus.

The system has a few drawbacks. It can read text messages but not e-mails, and you can't use it to add or edit phone contacts. Also, instead of speaking directions, it displays a map on your phone.

Perhaps the biggest drawback: Siri works with a limited number of third-party apps. That's where Vlingo excels. I tested the app on the Samsung Galaxy S II, an Android smartphone. To get started, I opened the app and hit Speak It. To post a status update on my Facebook page, I said "status update," and a list of social networks popped up. I chose Facebook, dictated the update, and clicked an icon to post it.

To research hotels for an upcoming vacation, I said "trip to Chicago," and Vlingo opened the Kayak app on my phone. (The destination field was already filled in, but I had to type in the rest of the information.) Another great feature: If you are using a BlackBerry or Android phone, Vlingo can read incoming texts and e-mails automatically. The app read incoming messages accurately, but the ones I dictated contained more errors than with Siri. Another downside: Vlingo doesn't send location-based reminders.

My verdict? If you're mostly interested in dictation, Siri is great. If you need a voice-recognition system that works well with other mobile apps, Vlingo is the way to go. But don't worry, Siri: I still love you.