One fun thing I like asking representatives from Nokia, Microsoft, or Research in Motion is “what does the post iPhone world look like?”

It is my way of sensing whether they’ve done any creative thinking. So far I’ve gotten mostly blank stares.

It’s like Steve Jobs has convinced everyone in the industry that nothing possibly can replace the iPhone on the coolest device shelf.

Me? I’ve seen this play before. Remember Sony’s Walkman?

I like pretending we live in a post iPhone world.

How do we get there?

Well, what would happen if we lived in a Twitter world? One where every light switch, every device, every machine, had a Twitter account?

I asked a Microsoft executive recently why they haven’t released a .NET/Silverlight runtime that Tweets.

His answer surprised me “have you signed our NDA yet?”

That’s code for “we’re working on just that.”

After all, Microsoft probably doesn’t like it that IBM has ruled enterprise marketing with its “Smart Planet” meme.

So, why would Microsoft support a Twitter world? Because if Microsoft helped Twitter build a world where everything has a Twitter API then Microsoft would also get the keys to the post-iPhone world.

“Huh?”

Well, let’s assume that Microsoft had .NET runtimes on everything. Right now I’m staring at an IV machine in the hospital room where our next son will be born. Why couldn’t a doctor Tweet that machine? Using a message that looks something like this:

@sequoia_iv_0451 set level to 1 pt per hour

That would change the drip rate on her machine to 1 pint per hour.

That doesn’t seem that important, does it? But now what if EVERY device in the hospital had a runtime like this and could be queried through a Twitter language?

Wouldn’t that open up new application possibilities that don’t exist today? Absolutely!

Wouldn’t that encourage new kinds of devices to be built? Absolutely!

Wouldn’t that mean we’d need a replacement for the iPhone? Absolutely!

Why? Well, let’s put it this way. If you had tons of devices in your world that you wanted to interact with TweetDeck or SimplyTweet just wouldn’t cut it.

Now, what if Microsoft made such a Twitter system more reliable? After all, if a doctor is going to have a device that will talk to all sorts of machines during surgery there can’t be a possibility of a fail whale.

Once Microsoft got .NET runtimes out in enough things they could come in and build a shadow Twitter that’s more reliable than Twitter and that has some cool features.

Then once that’s done Microsoft could ship a post-iPhone world. Why? Because they would be able to build a device that would be optimized for this Twitter world.

Oh, OK, this is all science fiction. After all it’s preposterous to think that the iPhone won’t stay on the coolest device shelf forever.

Right?

Go back three years ago. Twitter was being used by the same crowd that is playing with Foursquare today.

What is Foursquare? It’s a location game. When I visit somewhere, like Sequoia Hospital, where I’m hanging out with Maryam (we’re having a baby sometime in the next 24 hours) I check in on Foursquare.

What does that do? It gives me points and lets other people know where I am.

It sounds really lame, doesn’t it? But didn’t Twitter sound really lame to you when someone first told you about it?

It’s not lame.

Already I’ve met people because of the game and it’s weirdly fun.

The game gives you points for doing various checkins. If you do a lot of checkins everyday you get more points. You also get badges (which are sort of like achievements on Xbox games) for doing various things. For instance, I checked in so much at the Half Moon Bay Ritz that I became the Mayor of that location. It’s a lot of fun and great bragging rights.

Yeah, still sounds lame, huh?

But I think this lame little location game is going to be bigger than Twitter.

Why? Because eventually businesses will learn that this is an even better way to engage with customers than Twitter is.

Why? Because when you know your customers location the way this game is going to let you know you can really do some wild offers. Plus, I bet that they add in their own Twitter-style feature that will let people talk with each other.

I wonder if Twitter will build in its own version of Foursquare into Twitter? So far Twitter hasn’t built in any location-based services (other than to add in a new API which has yet to be turned on in any real way) so who knows?

Either way, this thing is growing remarkably quickly, just like Twitter did back in 2006. Now that Foursquare has funding, too, I expect to see more cities and more features turned on.

Why is Foursquare more useful than, say, Google’s Latitude? Well, you choose the moments and places you check into. With Latitude, if you leave it on and head to, say, an adult establishment, everyone will know. With Foursquare no one would know, unless you clicked checkin on your phone.

What about competitors, like Gowalla? I’ve been playing with Gowalla too and it doesn’t have the gameplay yet, which I’ve found is critical to getting me to use Foursquare. It also doesn’t have either the community (I already have about 1,000 early-adopter friends on Foursquare, but only a handful of friends on Gowalla) or the business listings that Foursquare has (every place I’ve visited today was easier to find on Foursquare than on Gowalla).

The really scary thing is how FourSquare could become a much better Yelp than Yelp. Or will know more about me than even Facebook. Think about what the stores and places you go says about you! Think about the advertising Starbucks could do with you if it knows you go into a competitor for coffee every morning at about 8 a.m.!

I see all sorts of things that can come out of this little “lame” game. Twitter better watch out. I give Foursquare 400 more days before it is on Oprah.

How about you?