sim cards, credit cards etc. (in particular the chips) are compromised. So everything except what you encrypt yourself is not save even if it is "encrypted" by company X/Y, standard X/Y (phone calls for example). You "should" be fine as long, as you encrypt your conversations yourself (jabber, TOX, PGP...) and use https websites and such. The hostile baseband processor inside UMTS modules is worse.
Related to the Pyra, I don't recall hearing about a sand box design aproach like the Neo900. But since its the same hardware designer maybe I'm not up to date???