IEEE 802.15.4 is a standard targeted at low rate communication between devices over personal area networks. It can be tailored to accommodate low-end, low-power devices, as well as more powerful and feature-rich ones.
The standard only defines the lower layers. High-level protocols have to be designed to accommodate for the application’s requirements.
Despite its relative simplicity and the number of third-party libraries readily available, there are a number of pitfalls that you have to be aware of when deciding to use IEEE802.15.4. In particular, there is a strict duty cycle requirement (for EMC regulations), which considerably reduces the effective bandwidth. We have also found that the code quality of IEEE802.15.4 libraries was quite low, leading to vulnerabilities, or even actual bugs.
We have a lot of experience in implementing and debugging IEEE802.15.4 based protocols.