Why would you want to have your hardware wallet attached to your phone case? It's almost the same level of danger as carrying your Ledger/TREZOR on a keychain everywhere. If you need to spend some of your coins outside then simply transfer them to a good software wallet.
I assume this the point which bothers the most.
A mobile hardware wallet as a secondary wallet holding small funds does have quite a lot advantages over a mobile wallet.
Physical 2-factor-autentication can not be attacked via any network-/communication vulnerability at all.
On a smart phone on the other hand there are quite a lot vulnerabilities which can lead to a compromised phone.
Your whole security relies on the smartphone to be clean, which not a good assumption to make.
Regarding the poll, the device i'd like to see the most would be a mobile with an inbuilt (but seperated) hardware wallet.
