I don't think your examples are actual "passive voice". That would be more like:
I see the cake eaten by him.
She heard the bells played by the children.
I'd have to do some research to figure out what exactly your examples would be called (the gerund form of the to be verb, maybe), but in the right context, it should be fine:
I saw her being kissed
She saw me sneaking out of the party.
Your examples don't work, mostly because I don't understand what you are trying to say with "being connected". You can't normally "connect" a person, and objects normally are or are not connected, and not "being" in the middle of the process ... but now that I think about it, there are some cases where it's fine:
My cable service is being connected (the guy from the cable company is here to connect my cable).
Hold on, I'm on the phone being connected to a support representative.
Lastly, "that" is fine in your examples, although it's often unnecessary:
I see the cake that was eaten by him
She heard the bells that were played by the children.