I am currently using an Ottocast mini, but I have an AA wireless 2+ on order. The Ottocast was absolutely fine and I suspect some of the issues I see are actually to do with the car (though in my case, this is actually in an Audi A4).
I originally wanted the AA wireless 2+ as that seems to be the go-to for this purpose, it just wasn't generally available when I was looking. I can try to report back in a week or so once I've got it.