Trezor does not work on iPhone. They refuse to pay licensing fees to Apple I think. I would never keep private keys for more than a few bitcoin on an insecure device like a phone. You could just use Trezor with your laptop while on vacation. Trezor works with OS X 10.8 or better just not on iPhone.
I'm just wondering why I should trust a Trezor, as I trust Armory. With Armory, it's software on GitHub that I compile. With Trezor, it's hardware and I have no idea what they put into the hardware and I don't know much about hardware. So I'm kind of scared of it.
Are there any software alternatives to Armory that use SPV (so I don't have to carry the blockchain with me) but also have determinstic wallets (for one backup only)?
. All Trezor does is keep your private keys offline and sign transactions. Both Electrum and Multibit HD are lite wallets. Electrum has the option of cold storage using two computers like Armory, or you can use Trezor or Ledger with Electrum to sign.