In The Unicode Standard, Bopomofo implementation is discussed in Chapter 18 East Asia.
Bopomofo was first encoded in The Unicode Standard version 1.0. The script is now encoded in the following blocks:
Subsequent to version 1.1, the following characters have been added to Bopomofo:
Documentation refers to ISO Working Group and Unicode proposals
A number of proposals for its inclusion were submitted to the Unicode Technical Committee and WG2:
1998-03-19 Proposal to add 24 extended Bopomofo and 2 modifier letters for Minnan and Hakka languages in ISO/IEC 10646-1 — TCA ( WG2 N1713.rtf, L2/98-090)
2016-04-21 Proposal to encode one Bopomofo letter — Andrew West (WG2 N4717, L2/16-106)
UTC #147 Minutes ( L2/16-121) (See C.16 for decision and action items)