I hate how everyone is marveling apple and their "engineers" for all these easter eggs and for "creating Siri". It was completely developed by an outside company and listed on the AppStore. Apple saw its potential and quickly bought out the company and removed the application from the AppStore. Luckily, I was able to snag a download of it first before it got removed. The application I have does 90% of what the integrated Siri does in the iOS (can't do things like read texts, send texts and set reminders by location).
Although, I'm sure with an update and removal of a few restrictions it could. And the application runs great on my iPhone 4... Just goes to show you how "greedy" apple is, restricting features to make you get an iPhone 4.
Want proof? See my attached screenshot on my iPhone 4:
Apple buying out the company who made Siri would make those engineers Apple engineers, so they indeed made Siri