do you have any electronics experience?
If so, the Picaxe datalogger with a temp sensor could be the go
http://www.microzed.com.au/datalogger.htm
DS18B20 is code for the temp sensor
http://www.microzed.com.au/chips.html
It does require some soldering, the programing cable is a simple serial interface and they sell them. the software is a free download.
The system could log temps every 2 seconds with in it's standard form 512 readings, with the Real Time clock it would tell you what time the measurements where made.
I hope this helps
Neweyn
PS I dont have any affiliations with microzed or picaxe.