The first untethered jailbreak for the iPhone 4S and iPad 2 dropped two weeks ago, much to the excitement of the hundreds of thousands of people who rushed to download it.

Despite its recent growth in popularity, jailbreaking is still not a mainstream activity among iPhone and iPad owners generally. It's more for the tinkering type and those who want to customize their device's functionality and UI design. Whether it's done to download unauthorized (yet often quite useful) apps from Cydia or customize the look and feel of the OS, there are a lot of reasons why people jailbreak their devices. For iPhone 4S owners, that list is made all the more compelling by one thing: hacking Siri.

Tools like AssistantExtension lets you use Siri to open apps, modify settings, search for YouTube videos and post tweets. Taking things a step further is the forthcoming MySiri, a tweak for Siri that allows users to do things like adjust the phone's settings, swap out Siri's background and define custom commands for Siri to do a wide range of tasks.

Using a feature called Activator, users can verbally do things like lock the phone, turn WiFi and Bluetooth on, run a Spotlight search and much else. Activator lets you define your own customized requests, so if you want Siri to open a new email every time you say "Abracadabra," then so be it.

Tweaks like this begin to show the real potential behind Siri, as is often the case with features that only work on jailbroken devices. Apple ships a solid, but limited offering, and then developers get their hands on it and in improve. In many cases, some of the best new features find their way into Apple's next official release.

Even before the Absinthe A5 jailbreak tool was released, developers wasted no time modifying Siri to do things like start cars and adjust thermostats. Such cross-device hacks require coding skills, a third party service like SiriProxy and a compatible, Web-connected appliance to mess with. It can make a fun weekend project, but it's probably beyond what most users are willing to get their hands dirty doing.

This new breed of device-based Siri tweaks is much more in line with what the average user would likely be interested in using. If history is any indication, these may be standard features in iOS before long.