Hi Forsberg,
Measuring hotspots in a fluid would require several RTDs or thermocouples, a data acquisition system, and an analysis and data logging system. National Instruments has many data acquisition devices, signal conditioning to make temperature measurements, and LabVIEW software to analyze and present the data. You can find some recommended products and more information here:
Choose the Right Temperature Sensor
http://www.ni.com/temperature/right_sensor.htm
Recommended NI Hardware for Thermocouple Measurementshttp://digital.ni.com/public.nsf/allkb/F0196F5B6CD8F60286256D4B00728B78
Required Signal Conditioning for Thermocouples
http://zone.ni.com/devzone/cda/tut/p/id/4802
Taking Thermocouple Measurements
http://zone.ni.com/devzone/cda/tut/p/id/4237
Once you acquire data, you can then use LabVIEW to analyze it and present it in a meaningful way. LabVIEW allows you to completely customize this process for your application. Find more information about LabVIEW here:
NI LabVIEW - The Software That Powers Virtual Instrumentation
http://www.ni.com/labview/
If you would like someone to contact you with further information about putting together a measurement system, please post back and we can exchange contact information.
Regards,
John Bongaarts