GSM remote temperature monitoring/ logging


I currently monitor low energy buildings using temperature, power and CO2 sensors.  These are stand-alone units which log to an internal memory. Which is great if the person is in and you can collect the data - but not so good if they are out.

I want to take things to the next level and be able to collect temperature and power logs remotely.  There are bits of kit on the market which do this - but the cost is prohibitive (£1,000+).   There are also various other cheaper GSM based products on the market for GPS trackers, car sensors, home monitoring etc...

Is anyone out there clever enough to suggest cheap modular components that could be combined to:
1 - sense a temperature
2 - log the temperature
3 - periodically send the file via a mobile signal

I'm up for doing the work  if someone can point me in the right direction - or very happy if some has already done it!

Many thanks