That is wikkid! Great idea, would have been pretty simple to implement, wish I'd thought of it after doing my on tilt shift stuff. I thought I made a thread about it but I can't find it now :(
I think I remember you asking how to do them in The GIMP or something, yeah?
The thing with tilt shift is if all the site does is add a mask & blur above and below it, it will only look really good on certain pictures. That boat one is an example of one that doesn't look quite right because the building in the foreground is on a different focal plane to the boat so it needs to be masked off and blurred even though part of it protrudes up into the section with the boat. Same with the rocket/missile.
I agree with what whoop is saying - even though they're my images, because when you're using the website it can only do it so wide, like it has a maximum. I could make them look better but that would take too long than I care to spend on this stuff, even tho I think it's awesome. doing it properly I could make the field which is in focus wider. using the website you have to choose pics that fit right with their settings.
The car I did above, was done in Photoshop. Just selected the upper and lower regions of the images and feathered them by a large amount. Cut out the car from the selection and then blur repeatedly until you get the desired result.
Reason for large feathering: When you add in a little Gaussian blur and repeat it, the "lower or closer" and the "upper or furthest" parts of the images will blur more than the areas closer to the car.
Still didn't turn out that great, viewing angle was too close to the ground.