feedrecentchanges days is too coarse. Please also add a seconds parameter.
(From the viewpoint of seconds, you only allow 86400, 172800... seconds.)
Motivation: a cronjob that checks this daily
26 22 * * * GET http://radioscanningtw.jidanni.org/api.php?action=feedrecentchanges&days=1 |sed '1,/<item>/d'
but one worries about not giving it a few more minutes overlap day to day.
Also allow time frames, like UNIX find -mmin +22, -mmin -44.
list=recentchanges already could do this.