This! True crypto doesn't require any hardware at all. It's pure math.
(just keep an eye on partially sendings, missing return adresses)
Regarding a used Trezor for daily useage I believe it is totally secure. Reflash it, take a closeup look of the casing. Has it been opened?
The attack surface of those devices is really small. I would be more worried about other portable devices like dedicated cellphone since they arrive backdoored by manufactorer, or get a fresh backdoor upgraded via wireless update. Stealing data from phones seems to be common practise, everybody is trying that.
They got invented for stealing data.
Thanks!
So it seems I can be more secure if I use the second hand Trezor like a hot wallet and a brand new for bigger amonunt and forget about web based mobile wallets...
Something else:
I had a look at the official shop of Trezor (https://shop.trezor.io)
It seems that they're out of stock now (every colour)
I had a look at amazon too, but the price is double (!) compared to the official shop...
on trezor.io, you can get $99 + shipping, on amazon, it's nearly $200
Seems I should wait for the official shop, they estimate the delivery for March 2017...
(it seems that there's no Trezor on ebay at the moment...)
Found a new webshop where they accept Paypal and you can buy Trezor, it seems like an official bitcoin webshop.
Do you know it, have you ever bought anything from them? Is it a trustable?
https://store.bitcoin.com/collections/hardware-wallets/products/trezor?variant=19194849091
The price of the Trezor is the same as in the official Trezor webshop, but at Trezor's shop you can only pay with bitcoin.
Amazon is far too expensive