Comment by averageRoyalty

> Or is there more middleware required to connect the two VoIP?

You need an address of record to translate 111222333 to an actual deliverable location, like a PBX. You can do without it in a software solution, but in the age of NAT having a TURN server is highly advised.

> I don't like it requiring an account.

Remember the value proposition here is for kids calling trusted contacts. You could absolutely and easily build your own VoIP network with Asterisk etc.