The Iron Man armor is often hailed as Tony Stark's greatest technological achievements, but he actually put a function in the products he sells to the public that is far more impressive.
At the height of his powers, the villain the Mandarin created Mandarin City and kidnapped Tony Stark along with Stark's rival Zeke Stane. The Mandarin hoped the unlikely pair could build gigantic robots that would house the entities that resided inside the Mandarin's ten rings. Ultimately, the Mandarin's plot was foiled, but not before it was revealed that Tony Stark's AI Jarvis was compromised and needed to be destroyed.
In the final issue of Matt Fraction and Salvador Larocca's run on The Invincible Iron Man (issue #527), Tony Stark has to deal with the ramifications of having something he created used for nefarious purposes. To prevent something like this from happening again, Tony designs a means for his tech to know when it is being repurposed into harmful configurations. However, he doesn't just do this for state-of-the-art things such as his armor and AI; Tony puts the feature in everyday products like cell phones. Tony reveals this after a disturbed man attempts to turn Stark tech into a bomb, only for the tech to both deny this use and contact Iron Man with the man's locations.
There are many others in the Marvel Universe that have armor and suits similar to Iron Man's, but no one has ever devised a mechanism to prevent their tech from being repurposed for something evil. This goes beyond anything any comparable inventor has created in the past because it requires the technology to have a level of sentience to understand what it's being used for. It's not that the tech can't be repurposed - Tony allows that - it's that the tech understands what it is being repurposed for and then makes a decision on whether or not it will continue to function.
This has huge implications for the future of the Marvel Universe, for both good and evil. A tech giant like Stark creating tech that can judge how it's being repurposed would likely have a vast knock-on effect on society, as various products can be limited and/or rendered 'safe' based on their creator's whims. The concept of this invention could change technology as it's currently understood, and introduce a host of legal problems it would take years, if not decades, to iron out. Impressive as his armor may be, this aspect of Tony's tech is likely to change the world on a day-to-day basis.
Besides the Mandarin's activities, it's understandable why Tony would want to create something like this. He faced a major trauma in his superhero career after being ousted by Norman Osborn, who then stole one of the Iron Man suits to become the Iron Patriot. After a short spell in which Tony's genius was co-opted by Osborn, the Mandarin, and his own AI, it makes sense he'd design the ultimate form of cyber security. However, in perpetually maintaining control of the tech he creates, Tony Stark likely created something which will change society far more than his personal Iron Man armor.