Two options, either (1) get an iPlayer slot-1 card which has its own CPU and somebody made a GBA emulator dedicated to that card only because of the CPU. Or (2) get an EZ 3-in-1 slot-2 card which is compatible with AK2(i) + AKAIO.
Those are basically the only options left to emulating GBA games on a DS. For a DSi the first option is all there is.
Unfortunately yes. =\. But I'm told that it emulates most GBA games nearly perfect.
BTW: I meant DS iPlayer which is how most sites market the card.
Also, costs are:
(1) is around 35 dollars give or take in what site you use.
(2) is around 19 dollars more or less depending on the site.
These are based on the prices on Dealextreme.com (slow (from Asia) but free shipping and the lowest price around)