VOX actuator for baby alarm

Having a recent arrival in the family meant that some form of baby alarm or monitor was required if 'junior' was not to 'wah' unduly in his cot when left unattended. The circuit published seemed suitable, and was duly built. However, having dealt with single-transistor RF oscillators before, I was suspicious about the lang-term stability of the transmitter, and did not want to sit thinking a11 was well when 'junior' was actually 'washing away' a few tens of kHz further up or down in the FM band.