No, because proof-of-work prevents you from "faking" a blockchain. Let's say we are at block 100 and you would want to fake "the blockchain". You would have to fake a block every 10 minutes, but that requires mining, because you can't just make a block - it has to fit the previous one with the right difficulty.
You could stop sending new blocks, but that would alarm the endpoint because it will be stuck at block 100 (in our example).
It means if you could override the signal with your own AND had a lot of hash power, you could slowly drag down the difficulty of your fake chain and eventually it'd be easy to create. But indeed you must (assuming the device managed to see the real block chain at least once) do a lot of computational work to start with.
You could stop sending new blocks, but that would alarm the endpoint because it will be stuck at block 100 (in our example).
The Proof-of-work scheme is pretty innovative.