The "Download Now" link directs you to the iTunes App Store, where you must continue the download process. You must have iTunes installed in order to open the link, and you must have an active iTunes account to download the application. This download may not be available in some countries.
From Goodsquirrel Apps:
iTemp is a plain and simple, yet fun to use temperature converter for Celsius and Fahrenheit via two friendly picker-wheels.Pick any temperature on the Celsius wheel, and the Fahrenheit wheel spins automatically to the according value (and vice versa). iTemp is meant to be a nice and simple, yet user friendly tool for everyday life, not a sophisticated scientific application.It is made for tourists, desert hikers or siberia travellers, who read the local weather report and like to convert strange temperature values into familiar units. It's not meant for astronauts, vulcanologists, or any other scientist, who needs to convert e.g. extreme Kelvin temperatures, accurate to a minimum of 12 decimal places.iTemp converts Celsius and Fahrenheit only, and its temperature range is limited to real life values from cold Alaskan nights (-60 F) to hot kitchen ovens (480 F).Enjoy it.