Here is an easy solution to check the temperature of your remotely hosted server. New motherboards have some sensors which you can read out but even if you have slightly older machines there is a chance that you can monitor the temperature without additional hardware:
Harddisks with "S.M.A.R.T." support have a built-in sensor which you can read out with the command "smartctl -a /dev/hda" (for the first ide disk). No kernel changes are needed to do that. So if you know what the temperature of the disk under normal conditions is, then you can detect a failing air-conditioning or a congested power supply fan because the temperature will also increase in the disk:

193 Load_Cycle_Count 0x0032 253 253 000 Old_age Always - 379
194 Temperature_Celsius 0x0032 253 253 000 Old_age Always - 45
195 Hardware_ECC_Recovered 0x000a 253 252 000 Old_age Always - 0

The command smartctl is part of the smartmontools package:

There is also a small tool which reads only the temperature (not all S.M.A.R.T. parameters as smartctl):

#hddtemp /dev/hda
/dev/hda: ST94011A: 45 C
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Has anyone tested this with older hard drives such as systems manufactured between 2001 - 2002?