I think I have an excessive level of paranoia, because I rejected all general purpose computers (like phones, tablets, etc) because they are too connected. I want something that ONLY knows bitcoin JSON over serial.
Whispercore will save your ass if someone physically steals your phone, but I don't think it'll help if the phone gets owned from the inside.
Yes, there will always be dangers like malware and wire(less) intrusion. Usually one can afford to lose money that is in a wallet, especially if it is you have it on your person.
I think buying a cheap android device dedicated to the bitcoin wallet app could be a fairly good wallet. If you make sure everything is encrypted, enable 3G (or WIFI/Bluethooth/NFC) on demand, all other radios disabled and with a secure screenlock it would be pretty safe. A data self destruct mechanism could also be implemented.