I misread this, I didn't realize MZMcBride is talking about RecentChanges. How unreasonable would it be to call ChangeTag::AddTags('mobile', $rc_id); for mobile edits? On first blush, the only major consequences is extracting the data since it'd be buried in a ts_tags blob?
Why would you look at ts_tags? change_tag table is much easier to pull out as it uses a more normalized layout.
-bawolff