You could do that with unity, but would be much easier with just html/javascript or others…
(building those form elements with unity would take some time also…in html you have lots of ready components to choose from, with full functionality already…)
Yeah normally I would simply create the form in html, style it with css and do the rest with PHP. But how do I make an application from that for mobile devices? Unfortunatly, PhoneGap doesnt support PHP.