It would be wonderful if the app would just tie into the new common Inbox for iPhone mail, but it can't due to Apple restrictions. Instead, you need to set up a connection to an existing email account in the app. Setup of the email account is generally very simple. Both for my MobileMe account and for a Gmail account with a custom domain name, all I had to do is enter the email address and password and Text'nDrive Pro did the rest of the work. Text'nDrive also detects Hotmail and AOL email accounts and will automatically configure them to work with the app. The service sends you a test email from your default account so that you can try out the service immediately.

Once Text'nDrive Pro grabs a new email from your inbox, it reads the first 450 words of the message to you. You're then prompted to either say "Reply to the message" or tap once on the screen to set up a reply recording. To end the recording, you either tap on the screen again, or you can just stop talking. You're then prompted to send the message. If you say "Send it now" or tap on the screen, the message is sent. You can also tap on the screen when Text'nDrive Pro is doing its 120-second countdown between trips to the mail server to have it check the server immediately.

So, how do the replies look? Well, a better answer is "how do they sound?" The replies are not transcribed and converted to text. Instead, your recipient receives an email that contains a link to the recorded (MP3) message, and they can listen to it. The sound quality was great when I was testing it in my office, but as one would expect it contained some background noise when I was trying it out in my car.

I found Text'nDrive Pro easy to use and set up, and it worked properly from the first minute I had it installed. I did have an issue a bit later on where messages were not being found and read. It then occurred to me that my Mac was downloading those incoming emails into Mail.app before Text'nDrive had a chance to read them to me. If you intend to use Text'nDrive while you're mobile, be sure to quit out of Mail before you hit the road, otherwise the app won't gather and read a lot of your messages.

Sometimes I wouldn't receive email that I was sending for test purposes. I think what was happening is that Mail on the iPhone was receiving the messages and downloading them from the server before Text'nDrive could have a chance to see them. It would be nice to see some information in the app describing how to set up email accounts to work more effectively with Text'nDrive.

If you don't want to reply to your emails but would like to listen to them, there's a free version of the app called Text'nDrive Lite. All it will do is grab email from one account and read it to you; you can't reply to them. It's also limited to reading the first 45 words of a message.

One thing to remember is that your iPhone is going to have to remain on while Text'nDrive Pro is running. If you shut off your iPhone, the app will continue to do the 120-second countdown between looks at the inbox, but it won't actually do anything else. If you're going to be using this on a regular basis in your car, investing in a powered dashboard mount might be a good idea. Text'nDrive Pro also doesn't work in background on iOS 4, so there's no way to use a navigation app in foreground, for instance, and have Text'nDrive pop up with emails when they come in.

Is Text'nDrive Pro worth $19.99? If you avoid even one traffic citation for "texting while driving," you'd probably come out ahead. If the app keeps you from having a bad accident while you're distracted by your iPhone, then it's worth every penny you pay for it, and more.

I'd like to see future versions add some functionality. First, I have 5 email accounts set up on my iPhone. I'd like Text'nDrive Pro to check all of the inboxes, not just one. Second, I'd love the ability to have it read SMS messages to me and let me reply to them without touching the device -- Hands Free Software says this is in the works. Next, I'd like adjustable voice prompts. While the prompts are very detailed and complete, they're going to get pretty old after a while. I'd like to be able to change to a "terse" prompt, in which Text'nDrive Pro would ask "Reply now?" and I could just reply with "Yes." Instead of telling me to either tap the screen or just stop talking when I'm done reply, it would be nice if the app would just let me do that -- after the first time I used it, I knew that's how I finished a reply. There's no need to repeat the prompt to me every time.

One other future enhancement that would be wonderful would be the ability to have the app monitor Twitter, read incoming tweets, and then let you use the reply mechanism to answer the tweets.

As it is, Text'nDrive Pro is good -- with a few enhancements, it would be excellent. By the way, if you're a TUAW reader who doesn't own an iPhone but does use an Android or BlackBerry device, you're in luck -- Text'nDrive is currently available for BlackBerry and will soon be on the market for Android as well.

One final note. Even with an app like Text'nDrive Pro, it's best to remember that any action you take while driving, including just talking on your phone with a handsfree kit, is going to take attention away from the very important task at hand. It's best to just leave the talking, reading, and replying until you get to your destination.