Without an in-depth understanding of the environment you leave you bike in, it's hard to advise. I always lock my wheels with the same u-lock(s) or chain(s) I lock the bike with. Someone will state the obvious, that with bicycles you can never reach absolute security - that might as well be me in the first reply. Anyway, in security skewers there's the
Pitlocks and the
Pinheads.
Bicycle Bolts offers security torx screws for seatpost, saddle and stem.