You can still get standard allen keys to work in most sizes of torx fasteners. Pitlock offers a solution for seatpost and stem (top) bolts with a keyed fastener.

Personally, I filled the seatpost clamp, seat clamp, stem top, and one handlebar clamp bolt with shoe goo, then topped off with superglue. A bit of picking will get it out, but it'll take longer than most casual thieves would be willing to deal with.

Note: Using full superglue is commonly recommended, but will require the use of acetone or major patience with a small sharp pick to remove. By using shoe goo, which is flexible, beneath the superglue it is easier to crack the coating of superglue if the bolts need to be removed. It still sucks enough to hopefully deter theft, but it sucks less than full super glue. The thieves will hopefully see the superglue layer on top and move on.

I'm currently working on a way to keep my wheels on without needing a cable or second lock.