Need to know when we last had an in-person meeting with a contact or lead. Salesforce allows you to track this information as a task or event on the contact or lead record, but to trigger workflows, validation rules, otherwise show this metric on the lead/contact detail page you would need to write custom code. The solution is Rollup Helper.
1) Create target field that is a date field on the contact and/or lead object.
2) Create a rollup, selecting target object contact/lead and then select your target field.
3) In step 3, select the source object task / event (depending on type of object); choose relationship field that applies; and then select activity date field. Choose MAX rollup type to grab the latest date found.
4) Create new filter where:
a) subject contains In Person Meetings
5) Click save and run (or upgrade to get real-time)