From the Bitcoin wiki:
Suppose Alice wants to send a bitcoin to Bob.
1) Bob sends his address to Alice.
2) Alice adds Bob’s address and the amount of bitcoins to transfer to a message: a 'transaction' message.
3) Alice signs the transaction with her private key, and announces her public key for signature verification.
4) Alice broadcasts the transaction on the Bitcoin network for all to see.
Some considerations for TinCan:
Step 1 could be done with TinCan, just like using e-mail or postcard or skywriter. Security is not important, since Bob sends his public address (e.g. something that looks like "1Krn7vC1kqmag8wbTbr1yZCJceHYVmpYse").
Steps 2-3 would normally be done using dedicated bitcoin software. Someone who has bitcoins to spend is likely to have an app or software to generate transaction messages. So there isn't a strong reason for TinCan to take on this task and try to convince users that it is reliable and trustworthy.
Step 4 requires access to the worldwide bitcoin network, and the transaction will not be verified until it is broadcast. So the selling point of TinCan -- that it works without Internet access -- would render this step impossible.
In other words, without modification TinCan could be used to share one's public address in order to receive funds later. This might be useful in the protest or concert or natural disaster scenarios for small purchases based on trust, or else to solicit later donations while passing out water bottles or gas masks.