I just realized that my suggested approach above is not secure. Revealing the locations in the message is not ideal. In my example, should a hacker gain access to the message I used as an example, I think I would simply end up with two break-ins, or broken windows on my vehicles. Or if someone were to discover half a paper bitcoin in one glove compartment, that person might just go check the other vehicle for the other half. That just wasn't a very good suggestion.
After reading their FAQ, I can now see there are better ways:
Is this service secure?
To ensure that your messages will not be read by anyone other than the intended recipient, the messages are only ever stored securely on our servers. The messages are destroyed after they are sent, and you can delete them at any time.
If this is not enough, you can encrypt your messages using symmetric or asymmetric encryption using widely available software like PGP or GPG. This will ensure that no-one other than the intended recipient will ever be able to see the contents of your message.
Instead encryption is probably the best.
And GPG works well for that.
So to spend the funds there are three components,
1.) An encrypted file containing the wallet's private key for the Bitcoin address holding the funds. This can be ASCII (armored), and will be about 600 characters long.
2.) An export of the GPG secret key as ASCII (armored)
3.) The GPG passphrase for decrypting
So to the executor I give #3 (paper/text) and #1 (paper/ASCII - armored).
For the message on DeadMansSwitch.net I have #2 (file/ASCII - armored) and #1 (file/ASCII - armored), and that goes to both the executor and the reporter.
To a trusted party / family member, I give a thumb drive with #2 (file/ASCII - armored) and #3 (paper/text) with instruction to store securely and give to executor after I pass.
Default condition: The executor already has #1 (file/ASCII - armored) and #3 (paper/text). Trusted party / family member hands over to executor #2 (file/ASCII - armored).
If trusted family member fails: The executor already has #1 (file/ASCII - armored) and #3 (paper/text) and after 60 days of my last checkin gets from DeadMansSwitch.net #2 (file/ascii - armored).
If Executor fails: The reporter gets from DeadMansSwitch.net #1 (file/ASCII - armored) and #2 (file/ASCII - armored) and trusted party/family member hands over to reporter #3 (paper/text).
This pretty much eliminates the risk from a hacker as the executor only has paper copies of #1 and #2, and hacker doesn't know there is a trusted family member with #3 (and even if somehow did discover this, the thumb drive would be stored securely, offline.)
Getting closer here I think.