Need to know how many times we had an in-person meetings 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 number 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 deleted field). Choose COUNT rollup type to count all records that match your filter.
4) Create new filter where:
a) subject contains In Person Meetings
b) activity date greater or equal last 365 days
5) Click save and run (or upgrade to get real-time)
6) Add a schedule to the rollup to run the roll-up daily as every day an in person even could be older than 1 year old and need to adjust your count to exclude that in person meeting.