How can I convert full-width characters to half-width characters (and vice versa)?

Here is my simple problem, how can I convert half-width to full-width from the command line. I thought this would be built-in my iconv command line, but I did not find anything here:

$ iconv  -l | grep -i full
-> nothing
$ iconv  -l | grep -i half
-> nothing

Typical input would be:

$ echo -n "Ａb９８７６５４３２１０" | iconv -f utf8 -t utf16be | hexdump -C
00000000  ff 21 00 62 ff 19 ff 18  ff 17 ff 16 ff 15 ff 14  |.!.b............|
00000010  ff 13 ff 12 ff 11 ff 10                           |........|
00000018