There's a new flash cart for the Nintendo DSi and it's called the R4i. You should know that all the current flash carts don't work with the DSi except for the Acekard 2i, the R4i and the R4 for Nintendo DSi.
Many websites are now selling these Nintendo DSi compatible flash carts but many are still asking if they actually work. Here are some videos to answer your questions about the R4i for Nintendo DSi and other flash carts such as the Acekard 2i and R4DS.
A video proving that the R4DS doesn't work on DSi but English games will work on the Japanese models.
Here is a video where it shows that the Acekard 2i is working for the Nintendo DSi. It can also read and store data on MicroSD cards in the new slot and run homebrew and DS Roms.
Here is a video showing that the new flast cart R4i for DSi really works.
The Nintendo DSi is now selling at US$169.99. It is available in black and blue colors. DSi has two 0.3 megapixel cameras, larger screens, a new SD card slot and better speakers. However, the Game Boy Advance cartridge slot is gone.