If points equal value: reset to zero I use the User Points module. I've set a rule that add 10 points per content viewed. This was easy. THEN I want to check if user points is greater than 100 and, if it is, send an email to admin, AND set points to that user back to zero.
Download the Rules module and import the following rule:

{ "rules_reset_points" : {
    "LABEL" : "Reset points",
    "PLUGIN" : "reaction rule",
    "OWNER" : "rules",
    "TAGS" : [ "Points" ],
    "REQUIRES" : [ "php", "rules", "userpoints_rules" ],
    "ON" : { "userpoints_event_points_awarded_after" : [] },
    "IF" : [
      { "php_eval" : { "code" : "global $user;\r\n$num_pts = userpoints_get_current_points($user-\u003Euid, \u0027all\u0027);\r\nif ($num_pts \u003E 100) {return TRUE;}" } }
    ],
    "DO" : [
      { "userpoints_rules_get_current_points" : {
          "USING" : { "user" : [ "userpoints-transaction:user" ], "tid" : "all" },
          "PROVIDE" : { "loaded_points" : { "loaded_points" : "Number of points in the specified category." } }
        }
      },
      { "data_calc" : {
          "USING" : { "input_1" : [ "loaded-points" ], "op" : "*", "input_2" : "-1" },
          "PROVIDE" : { "result" : { "result" : "Calculation result" } }
        }
      },
      { "userpoints_action_grant_points" : {
          "user" : [ "userpoints-transaction:user" ],
          "points" : [ "result" ],
          "tid" : "0",
          "entity" : [ "" ],
          "description" : "Prevent more than 100 points.",
          "operation" : "Add",
          "display" : 0,
          "moderate" : "approved"
        }
      }
    ]
  }
}


Adapt the actions to your needs, add another action "Send mail" after installing the Mime mail module (this article may help you in doing that) and you're done!