I'm pretty sure that XM (Sat Radio) does have a signal meter,
AFAIK. Its in the header bar above the app, below the top big header. I don't have XM installed here, but you may have to touch it to toggle it, but I swear i remember it shows both Sat and Terrestrial signal strength. (eg. S - 3 / T - 2) or something like that. Scott or someone else can correct me if i'm wrong.