This demo use form rules and metadata so you can change the video displayed. The form rules generate dynamic HTML to render an iframe containing youtube videos.
Keenforms also let's you generate dynamic HTML, which is a feature that no other form builder has.
More info to come
There are lots of mortgage calculators online. At some point I wanted to see if it was possible to build one using another form builder, but was ultimately unsuccessful. Many form builders allow for calculated fields. However calculating a monthly mortgage payment requires a higher degree of precision than what was available.
So I decided that keenforms would be capable of doing just that. The formula for calculating a monthly mortgage payment can be found here. There are a few value setting rules that break the calculation into small parts. One rule calculates the monthly interest rate from the yearly interest rate. Another rule calculates the number of payments by multiplying the years * 12. A rules engine makes that possible.