Nowadays we can find RFID technology almost everywhere: in supermarkets (anti-theft), in assembly lines (identify & track items), in highways (tolls), in public transportation, in your passport and your credit card and it is also used by many companies and by hotels for access management.
This post is about the latter. Indeed, during my trips, should it be for business or for holidays, I have stayed in many hotels. Some of them were still using good old keys like you do at home, most of them still use magnetic cards and some were relying on RFID cards to give you access to your room. Unfortunately, the security level of such RFID access management highly depends on the manufacturer as we will see.