measure temperature of hotel refrigerators

I have a customer who asked me to find what is the best, reliable and cheap solution for logging temperatures. My customer has already an old system that wants to replace. The question is if I should buy a plc, system like climate cm-2 or build something new with a microcontroller. He told me that he's ready to take the risk of a new and untested system and asks for the cost. So... I need the design (info on how to connect) and the software that measures the temperature of the big refrigerators (more than 10m2 each) a hotel uses for keeping customer's food. As a hardware we can use arduino or rapberry pi. Any other suggestion is welcome. I need at least 12 sensors. The software (web based) should : Log everything, Display the temperatures on a web page (with history chart for each fridge). Colors of display should change if temperatures are out of range. Alert by sending email if a temperature drops below a default value. Send the day's log to email Connect to a services like [login to view URL] (Bid does not include any hardware).