This project has been designed according to the following requirements.

• The system must remotely collect measurements without any need for a person to visit a location. Therefore, the system must recover from any fault without human interaction. The user interface is very simple, plug it in and walk away.
• The cost of manufacture should be very low. Therefore, the system is built from cheap components that can be bought from multiple online stores.
• The cost of operation should be zero. Therefore, this system uses a free cellular data service from Hologram that is available worldwide. Also, the web site is designed to be hosted by a free web hosting provider.
• Because the free Hologram service is limited to 1M bytes per month, this means that the data usage is limited to 1300 bytes per hour. Therefore, only one effort is made each hour to report a measurement. There is no attempt to retry in case of failure, because this could accidentally exceed the hourly limit.
• It should be possible to read the measurements without any special effort or training. Therefore, the measurements are presented in a web page which is accessed through any web browser.
• The system should operate for many years without intervention. Therefore, old data is automatically removed from the database to prevent overflow.