How to measure body temprature and HBR with just one IR transmitter and receiver
"IR" refers to a range totally different wavelengths, which need totally different materials to detect and even to be transparent to.

Pulse rate: 


Near-to-visible IR (NIR) 0.9um, 
transparent to skin, can see inside
sensing done by reflection: LED emits NIR, travels into body reflects off blood vessels, and back out to Photodiode


Temperature sensing: 


5-10um Thermal IR (TIR), 
measures heat emitted from skin surface 
emission energy proportional to surface temperature
does NOT use an LED emitter. skin IS the emitter


You need different devices.

Why?

Photodiodes (NIR and Vis) work by converting photons to electrons. This doesn't work at TIR as the silicon becomes transparent beyond 1.1um and doesn't capture the energy. (From another perspective the TIR photon energy is too low)

TIR Temperature sensors tend to work by the incoming TIR energy heating up the sensor, and measuring the relative temperature change. This makes them pretty slow reacting. 

It is possible that your skin temperature pulses with blood flow, but seems likely that the sensor will be too slow to track this. Even more significantly, your surface temperature is probably well low-pass filtered by the blubber layer and changes slowly - the temperature ripple has very low amplitude after filtering.

Someone else may know more about the transparency depth of TIR into skin.