Detect mobile and redirect to mobile website

The main website is on a Windows server, pages are written in html. I also have a .mobi website. I want the pages on the main website to detect if they are being called by a mobile / smartphone / Ipad and if so, automatically redirect the user to the appropriate page on the .mobi website. The solution also needs to be able to identify when a web page is being crawled by Google / Bing etc and be able to differentiate between their mobile crawler and their normal crawler. I have good html experience but very little knowledge how to achieve a solution to this requirement. I think that I only want the solution for one page - I can then implement the solution myself on all the other pages - unless you can additionally suggest a way to automate the solution to all other webpages. This website has about 1,000 pages. Excellent spoken English is essential to understand the requirements. The solution needs to be easily updated if neccessary to include new mobile devices.