Some cameras take them. The iCN range accept SD & MMC cards.
The iCN has 64MB of internal memory but some maps are larger than that so would require and extra memory card. They are installed to the card through the software supplied with the iCN so you need a PC for that.
Cards come in a wide range of sizes from 16MB to 1GB. You can see what we offer @
http://www.totalpda.co.uk/section310.aspx .