One of the most exciting things about the iPhone 4S for ditto’s Tech Lab, is the new Siri assistant. It is truly revolutionary and will change the way in which we use smartphones, mobile devices, and possibly even computers forever. A bold statement, but Siri deserves it.

You activate Siri by holding down your home button, much like you already do (or don’t) to activate Voice Control in iOS 4. From there you can speak to Siri and ask it questions. If it needs more information, it will respond to you with additional questions until it’s ready to provide the information or carry out the task you’ve requested.

If you want to know what the weather’s like, where to find a good restaurant wherever you are, the current price of a stock , the square root of 500, and much more, Siri can find that information for you. Among its sources are Wikipedia and Wolfram Alpha, providing a wealth of useful information. Ask it how many days until a given holiday, what’s on your calendar, or seek out pretty much any information you could want.

Siri can read you your text messages, or any other notifications in the notification queue on your phone. This is really handy when you’re in the car and receive a message you can’t look at. Siri can also compose and send replies based on voice input as well, so you can have a text-based conversation without ever touching or looking at your screen.

It also knows what’s in your address book and calendar, so it can easily inform you about your appointments and even add to them. Just tell Siri what you want to do and when, if you need a reminder, and it’ll add it to your calendar or reminders. If you’re using iCloud, that appointment will sync across your devices right away.

So what about kind of questions that we really want to know the answers to, such as the meaning of life, or where we can bury a body? Thankfully, a new blog aptly named http://shitthatsirisays.tumblr.com/ is getting those answers for us.

It’s still in the early stages of development, but already published are a number of conversations with Siri that have hilarious outcomes. You’ll be surprised what kind of response Siri gives to some requests, such as “Where can I get some drugs?” and “Who’s your daddy?” I’ve posted a few of my favorites below.

Siri is a feature of the iPhone 4S, so unfortunately it won’t come as part of a free update. Whether it requires the A5 processor or Apple just wants another reason to get you to upgrade is unknown, but either way current iPhone users are out of luck. Hopefully we’ll see Siri come to other iDevices in the future.