Can it transfer fractions of the wallet? If not can it have multiple addresses of small amounts?
"Fractions of the wallet" - yes. "Fractions of a key" - no. Keys (and their associated balances) are transferred altogether, so you cannot transfer less than a key (that would effectively mean you are sharing it with someone else and the whole point is to make sure the key is only held by a single person at any given time). If you need to "break" a key into smaller amounts, you can easily do so through the Bitcoin network - transfer the key you want to split to the Bitcoin wallet, then fund two (or more) OtherCoin addresses from it with any values you need. This is also how you can pay the exact amount requested = you pay the majority in OtherCoin, then if the merchant wants to receive _exactly_ what he's asked for, you either pay the rest via Bitcoin or you break an OtherCoin key into two smaller ones, then transfer one to the merchant (for the remaining amount to pay).
To ease the use the smartcard key exchange for purchases I envision that it would be best if people had many wallet keys (from now on I will call them coins) with balances of standard denominations (example denominations: 1 uBTC, 10uBTC, 100uBTC, 1mBTC, 10mBTC, 100mBTC, 1BTC, 10BTC, etc) so that they can give the exact amount or be given return change by totalling multiple coins in the manner similar to normal fiat eg: to give 0.8253BTC use 8x100mBTC + 2x10mBTC + 5x1mBTC + 3x100uBTC. You could quickly top-up your smartcard with more coins by asking other people directly for change or using a change service over the internet.
By-the-way Drazvan, this is what I was going to write an email about to you a couple of months ago. I am now sending a PM with some further details that you may be interested in.