Enumeration can do most of what you're after.
\setupinteraction[state=start]
\defineenumeration[todo][list=todolist,title=yes, listtext={Todo }, before=\startframedtext, after=\stopframedtext]
\starttext
\placelist[enumeration:todolist][width=8em,criterium=all, alternative=c]
\page
\input tufte
\starttodo[]{You must remember this.}
You can add details about what to remember here.
\stoptodo
\page
\starttodo[]{Unforgettable.}
\stoptodo
\input knuth
\todo[]{Important things.}{}
\stoptext
You might be able to get the final list at the end using blocks.