in the file Who.english.php in Themes/default/languages
you can add any extra actions so they show in whos online
these are some I have added, but they are only related to my forum
$txt['whoall_gb'] = 'Viewing the <a href="' . $scripturl . '?action=gb">Guest Book</a>.';
$txt['whoall_link'] = 'Viewing the <a href="' . $scripturl . '?action=link">Links page</a>.';
$txt['whoall_team'] = 'Viewing the <a href="' . $scripturl . '?action=team">Lesmonds team page</a>.';
$txt['whoall_magic'] = 'Playing <a href="' . $scripturl . '?action=magic">Magic 8 ball</a>.';
$txt['whoall_reco'] = 'Viewing the <a href="' . $scripturl . '?action=reco">Recomend us page</a>.';
$txt['whoall_gallery'] = 'Viewing the <a href="' . $scripturl . '?action=gallery">Gallery Pages</a>.';
$txt['whoall_State'] = 'Viewing the <a href="' . $scripturl . '?action=state">Privacy Statement</a>.';
$txt['whoall_Sudo'] = 'Viewing the <a href="' . $scripturl . '?action=Sudo">Sudoku</a>.';
$txt['whoall_tpmod'] = 'Viewing the <a href="' . $scripturl . '?action=tpmod;dl">Downloads</a>.';