How can I add an ammeter and/or voltmeter to my home breaker panel?
You're going to careen headlong into 

NEC 110.2. All equipment must be approved.

You want a conductive ammeter.  OK, because of the exigencies, that's going to be a large enclosure that will need to mount past your main breaker.  You can't insert that between your main breaker and buses in your panel, because your panel isn't listed for that.   That means changing to a meter-main outside the house, connected to the conductive ammeter equipment which is UL listed for this use, connected to your former main panel, which will need neutrals and grounds separated.  

"But you only need an ammeter shunt"  all of the above applies to the shunt housing.   

The ammeter equipment won't be cheap, because it'll be low production rate equipment made for industry.  I would expect it to be a triple ammeter intended for 480V, which is fine; use the third meter for neutral.  Are you sure inductive meters won't suffice? 

Nothing wrong with induction-based ammeters for measuring the current of a known frequency.

Which is to say, there is no reason to doubt ammeter readings merely because they clamp on.  

As such, a variety of consumer products provide exactly what you are looking for. The units are UL listed, obviously; they sit inside the service panel with clamps on the supply and also on some number of branch circuits.  The only thing that sticks outside the panel in a knockout, is a WiFi antenna.  Which elegantly solves another code problem, keeping mains and low voltage systems rigidly separated.  

That is the way to go.  The existence of these products will deter anyone else from offering plain old hardwired ammeters at a consumer price.