Due to the laws of physics, jamming in real time with anyone over the internet is and always will be next to impossible - barring a major breakthrough in quantum teleportation and entanglement.
Sessionwire's transmission of audio and video at high quality results in some latency that most performers would find distracting if attempting to jam or rehearse in real time. This is unavoidable and Sessionwire promotes workflows that accommodate this latency.
See the Common Applications section for discussion on how work using Sessionwire.
You can read a longer, more in depth article about why here.