You may have spotted a previous, unannounced, version of the Devanagari and Uighur pickers on the site, but essentially these versions should be treated as new. The Gurmukhi picker has been updated from a very old version.
In addition to the standard features that version 16 of the character pickers brings, things to note include the addition of hints for all pickers, and automated transcription from Devanagari to ISO 15919, and vice versa for the Devanagari picker.
For more information about the pickers, see the notes at the bottom of the relevant picker page.
About pickers: Pickers allow you to quickly create phrases in a script by clicking on Unicode characters arranged in a way that aids their identification. Pickers are likely to be most useful if you don’t know a script well enough to use the native keyboard. The arrangement of characters also makes it much more usable than a regular character map utility. See the list of available pickers.