I think it depends really on the goal you have with the temperature sensors. Michael (from http://mietz.imkerforum.de) included the sensors--I think it was some TI stuff with I2C--in the comb foundation. This may be good for (old) brood measuring, but is not helpful for monitoring small and fast changing temperature differences, e.g. as they occur in pre-swarming. The especially with honey cells coated sensors do react very slow, nectar / honey, pollen absorb temperature and so you will not get the real degree between the combs.