Hi all,
I wrote a Particle.io bridge and a gate opener example that allows for a Homespan device to control a cellular-connected Particle.io device (Boron 404X). If anyone in the community has a need to extend HomeKit beyond a Wi-Fi perimeter and would like to provide feedback, I would very much appreciate it. The Boron 404X Starter Kit is $50 but includes an activated SIM with no monthly fees.

https://github.com/Xorlent/HomeSpan/tree/dev-particle/examples/Other%20Examples/ParticleIO