Widely used as a surrogate measure of the impact of an author, h-index is controversial and, although it has a very simple formula, it is difficult to calculate it with high accuracy. The difficulty comes from the combination of databases limitations in content, citations accuracy, topic interdisciplinarity, and authors' name ambiguity.
h-index is readily available in Web of Science database. However, for scholars studying interdisciplinary subjects, or for those that do not have access to Web of Science database, Google Scholar may offer an acceptable substitute, although not without many caveats.
Additionally, metrics of the social media reach of publications or the peer-review activity could also contribute to creating a more comprehensive image of a scholar's academic impact.
Altmetrics
Keep track of social media activity surrounding your papers.
Credit for Peer-Review Activity
Peer-review is a common scholarly activity that is largely under-credited. These systems track and give credit for any submitted reviews.