This seems a little disingenuous to me. The implication of the first attack is not that someone might sneak into your house and modify your Ledger hardware. It's that hardware could come to you with modified firmware from the get go.
The obvious one is that the security domains in the device are idiotic. There's a "secure" processor with almost no processing power or IO, and a "insecure" one which handles the screen, buttons and IO. Both of them handle secrets (for example, the seed shown on the screen), which leaves you with essentially no gain whatsoever.
The more logical hardware implant than the one shown at CCC is a bluetooth module that can simply read the I2C lines going to the screen and transmit the seed as a beacon whenever it is plugged in. This has the advantage of not needing presence as with their demonstration, and with assistance doesn't need any physical presence.
I described this as a concept for a security review of a cold storage setup which was "unbreakable". Is this sort of thing realistic? Perhaps. Is a $5 wrench attack more sensible? Probably. It's worth considering what supply chain attacks are possible though.
I think the idea is that the secure processor will verify the insecure processor's firmware (the "MCU check"), making such attacks impractical.
Of course, the design is broken and it can be bypassed by emulation, but security isn't all or nothing - "no gain whatsoever" is not true.