OnRelay MBX is one of the vendors in Cellular Fixed Mobile Convergence (FMC) solutions.
OnRelay MBX delivers the functionality available on fixed enterprise PBX extensions onto a mobile device. MBX allows customers to keep their PBX (hosted or managed) but avoid the costly deployments of IP desk phones, allowing companies to replace some, or all office desk phones, with software and mobile phones.
MBX is a client-server software product.
Femtocells are an alternative way to deliver the benefits of Fixed Mobile Convergence. The distinction is that most FMC architectures require a new (dual-mode) handset which works with existing home/enterprise Wi-Fi access points, while a femtocell-based deployment will work with existing handsets but requires installation of a new access point.