A few new additions to this old module, available as of version 1.8.0 (session.txt import) and 1.9.0 (new API methods):
There's an option in ProcessLoginHistoryHooks module config to import login history from session.txt. This can be useful when adding this module to a site with existing history, since ProcessWire (by default) collects data about successful/unsuccessful login attempts to said log file.
This option is intentionally hidden under collapsed "advanced" fieldset. It's not super well tested yet, could result in a very slow request in case there's a lot of data to import, and in case disk timezone is different than the one in database duplicate records may be created on first run.
$this->modules->get('ProcessLoginHistoryHooks')->getUserLoginHistory($user, $start, $limit, $login_was_successful) returns login history data for provided ProcessWire User object. Default values are 0 for "start", 2 for "limit", and 1 for "login_was_successful", which means that by default this method will return latest successful login and the one before that. Return value is always an array; in case there are no results, an empty array is returned.
$user->getLoginHistory($start, $limit, $login_was_successful) does the same as previous command for a specific User object. All arguments are optional. This method returns a single timestamp (when limit is 1, or an integer value is provided for the "start" argument and "limit" argument is omitted), an array of login history, or null in case there are no results. By default timestamps for last two successful logins are returned.