For non-soldered but socketed BIOSes I think one can just take chip out and put it into your wallet, possibly, covering some pins with some dissolvable insulating substance. For soldered SPI EEPROM chips with known pinout, I think one can reflash the chip afterwards.
I had a Thinkpad T42 on which I managed to set a password for editing BIOS settings that I did not remember.
I the laptop into IBM for repairs to the monitor, and as part of their repairs they needed to get into the BIOS settings (I believe to run a diagnostic). Their solution was to replace the entire motherboard.
I was 99% positive the same could be achieved by messing with EEPROM. And, indeed, less than 10 minutes of searching yielded this unsurprising result: http://arduino.ada-language.com/recovering-ibm-thinkpad-t42-...
tl;dr: Nope, T42's BIOS password is not secure if you allow anyone with necessary hardware to touch the motherboard for a minute. TPM may (depending on the laptop model and firmware revision) prevent password recovery but will likely not prevent anyone from resetting them - at least this seems to be the case with Thinkpads. Next time I'll clean dust from my X300, maybe I'll remember this thread and check its EEPROM too. :)
So, do not rely on BIOS passwords as a strong security measure.
The technical expertise required to do so is very limited as long as you don't password-protect the BIOS: Basically, they only need to be able to plug in a USB stick and reconfigure the BIOS to boot from it.
In other words: If you leave your laptop outside of your physical control for even a few minutes, you may have to assume that it is totally compromised as long as you don't have a BIOS password.
If the laptop is outside of your control for a longer period of time, you probably have to assume that it has passed through the hands of somebody with sufficient technological know-how to work around the BIOS password as well.