[bencxr]

Even in it's current form, your grandma's wallet balance would resemble that of her BoA checking account, where the spendable amount would be a total of the easily-redeemable (Pay to pubkey hash) transactions.

More complex transactions would show up in more advanced wallets (possibly separately), and that is the way it happens in the real world now. Say you hold an options contract or a bond on some stock exchange - it's "spendable" but doesn't show up on your everyday bank account balance. This is useful money as we know it now. The allowance for such flexible transactions is a feature and not a weakness :)

[icebraining]

In fact, banks here in Portugal already show you two balances, an "accounting" balance which shows you the sum of all transactions, including ones that haven gone through yet (e.g. deposited checks) and an "available" balance which is what you can actually use right now.

It's really not that difficult.