Boost DC voltage converter for wireless temperature sensor (1.5V to 5V)
Your problem comes from the use of the LM35 temp sensor. You try to use that instead of a more appropriate choice, which causes you to include more circuitry.


Replace it by a sensor that works at 3V (LM75 clone? NTC?) and you can use a single LiSOCl2 cell... 
If you also select a uC that works down to ~ 2.5V you can use two AA cells
if you really want to boost a single 1.5V: google "boost 1.5V" (what else?) for some suggestions
or google "boost 1.5V dealextreme" ...