REST : users/online

:-) Yep, it is.  A user can be logged in multiple times.  We recently redid our Users Online widget and had to take this into account.  Here is the code we are currently using:

<div
	class="lia-panel lia-panel-standard UsersOnlineTaplet Chrome lia-component-forums-widget-users-online">
	<div class="lia-decoration-border">
		<div class="lia-decoration-border-top">
			<div></div>
		</div>
		<div class="lia-decoration-border-content">
			<div>
				<div class="lia-panel-heading-bar-wrapper">
					<div class="lia-panel-heading-bar">
						<span class="lia-panel-heading-bar-title">Users Online</span>
					</div>
				</div>
				<div class="lia-panel-content-wrapper">
					<div class="lia-panel-content">
						<div id="usersOnlineTaplet" class="UsersOnlineTaplet">
							<div class="lia-users-online-current">
                                <#assign member_count = rest('/users/online/registered/count').value?number />                                
                                <#assign guest_count = rest('/users/online/anonymous/count').value?number />
								<div class="lia-text">Currently online: ${member_count} <#if member_count <= 1>member<#else>members</#if> ${guest_count} <#if guest_count <= 1>guest<#else>guests</#if></div>
							</div>

							<div class="lia-users-online-recent">

								<div class="lia-text">Recent logins:</div>


								<ul id="list_0" class="lia-list-standard-inline">
								  <#assign seen_users = {} />
                                
                                  <#list rest('/users/online?page_size=5&restapi.response_style=view').users.user as online_user>
                                    <#if ! seen_users[online_user.@href]??>
                                      <#assign seen_users = seen_users + {online_user.@href:1} />
                                      <#assign online_user_ranking = rest(online_user.@href + '/ranking').ranking />
                                      <#assign avatar_info = restadmin(online_user.@href + "/profiles/avatar").image />
                                
									<li style="float:none!important;"><span class="UserName lia-user-name"> <img
											class="lia-user-rank-icon-left" title="${online_user_ranking.name}"
											alt="${online_user_ranking.name}"
											src="${avatar_info.url}" style="width: auto; height: auto; max-width: 64px; max-height: 36px;" /> <a
											class="lia-link-navigation lia-page-link lia-user-name-link"
											style="<#if online_user_ranking.display.color != ''>color: #${online_user_ranking.display.color}</#if>" 
                                            target="_self"
											href="${online_user.@view_href}"><span
												class="<#if online_user_ranking.display.bold == 'true'>login-bold</#if>">${online_user.login}</span></a></span>
									</li>
									</#if>
                                    
                                  </#list>

								</ul>
							</div>                            

							<div class="lia-view-all">
								<a class="lia-link-navigation view-all-link" id="link_147"
									href="/t5/forums/usersonlinepage">View All</a>
							</div>
						</div>
					</div>
				</div>
			</div>
		</div>
		<div class="lia-decoration-border-bottom">
			<div></div>
		</div>
	</div>
</div>

Note the seen_users hash to track those users we've already displayed.