There is a product that we have recently invested in called the Climate.
It sits in our server room and monitors temperature, airflow, humidity, light and sound.
For the cost it has more built in 'goodies' than others we looked at. The sensors all come as standard and since then we have bought some cheap add-ons such as external temp sensors which we use for other areas in the comms room.
All the data is presented in a graph that is displayed in its on-board website.
The alerts we recieve can either be in email or text format so i can even get alerts out of office hours. Dont quote me on this but I thnk the company is Swiftbase or The Climate, worth checking out anyway;
The Original Climate - Home
Hope this helps paperclip!