Among many other publishing innovations, JMIR was a pioneer in collecting and analyzing/displaying social media signals as an alternative/complementary metrics to traditional measure of impact such as the impact factor.
Specifically, JMIR was the first journal worldwide to systematically collect and display "Tweetations" (=journal article citations/mentionings in tweets) since 2008 (Eysenbach, 2011). Today, the number of tweets of an article is a part of what is known as "altmetrics" or an "altmetrics score" (which is now collected by our partner company altmetrics.com).
JMIR displays altmetrics as well as the actual tweets ("tweetations") on all its articles, in addition to citations (see screenshots below).
Research by JMIR has also shown that top-tweeted articles are more likely to be top-cited articles (Eysenbach, 2011), leading to the creation of the "twimpact factor" (tw7), which is defined as the number of tweets within the first 7 days after publication (which has been shown to be most predictive for later citations, if adjusted by journal). The Twindex is the rank percentile of a given article within the journal compared to the past 20 articles, in other words, a Twindex of 100 means that the article is top-ranked compared to previously published 19 articles in the same journal, Twindex of 95 means it is ranked 2nd, a twindex of 90 means it is ranked 3rd etc. A twindex of >=80 means an article is ranked 5th out of 20, i.e it is in the top 25% of articles by tweets after the first week of publication, which is highly predictive for this article to be among the top 20% cited within the same journal.
The Twimpact Factor and Twindex for each article from a JMIR journal can be viewed on the "top tweeted" page of that journal (for example, on https://www.jmir.org/stats/mostTweeted for the Journal of Medical Internet Research).