I want to understand if there is a Sena bluetooth that allows this. I couldn't figure out a way with another brand.

I understand I can pair a Sena with a phone and with a satnav. This way, I can listen to music from the phone, and hear directions from the satnav; when directions are spoken, the Sena lowers the volume of the music.

Is it possible to achieve the same using a second phone as satnav? So that I listen to music from phone 1 and to directions from phone 2? I have tried with another brand  but it doesn't work: I can connect two (Android) phones, but then I can only hear from 1 of the 2 devices, not from 2 at the same time the way I can with phone + satnav. If I listen to music from phone1 then I cannot listen to directions from phone2, and viceversa. Are Sena units the same in this respect?

By the way, I ask because my TomTom 500 has such an unstable bluetooth connection that it's basically unusable, and because smartphone apps have much better traffic data.