NRF24L01+ (RF Module) for Smart Home Device Communcation
There is only one scenario that I can think of when it makes sense to use these modules: To have a simple inexpensive reliable short-range wireless communication, especially unidirectional one, up and running quickly with Arduino libraries. Especially for small projects.

For anything more complex, especially with mobile phones, there's Bluetooth Low Energy. If you want to make a high-volume product for simple wireless communication, it'll be better to use an inexpensive RF transceiver like 
RFM75W.