The Nintendo DSi uses the same title scheme and update servers as the Wii, but they introduced a new (currently unknown) common-key for the DSi title decryption.
The following titles have been seen:
00030004: 484e474a ('HNGJ'), 4b41414a ('KAAJ'), 4b41444a ('KADJ'), 4b414d4a ('KAMJ'),
4b44394a ('K9DJ'), 4b47554a ('KGUJ'), 4b4d394a ('KM9J'), 4b4d464a ('KMFJ'),
4b4d534a ('KMSJ'), 4b4e444a ('KNDJ'), 4b4e524a ('KNRJ'), 4b50364a ('KP6J'),
4b54504a ('KTPJ'), 4b55574a ('KUWJ')
00030005: 484e494a ('HNIJ')
0003000f: 484e4c4a ('HNLJ'), 484e4341 ('HNCA')
00030015: 484e464a ('HNFJ') -- apparently the "firmware"
00030017: 484e414a ('HNBJ')
As with on the Wii, the TMD for these titles may be fetched at e.g. http://nus.cdn.t.shop.nintendowifi.net/ccs/download/0003000f484e4c4a/tmd.