If you are using SharePoint 2010, You probably have come across Business Connectivity Services (BCS) before. BCS is a set of services and features that connect SharePoint-based solutions to sources of external data. It is a powerful features of SharePoint 2010 to integrate various Line of business (LOB) systems like SAP, Siebel, SQL Server and of cause, PI System as well.
BCS was formerly known as Business Data Catalog in SharePoint 2007, and BCS is extended from BDC to support .NET assemblies and WCF services as data source(s), and adding feature to perform Create, Read, Update and Delete (CRUD) operations on the connected LOB systems. Another new aspect of BCS as compared to before is in the creation of the Business Data Connectivity (BDC) Model that defines how BCS should be accessing the LOB system to perform the required operations. There are now tools in SharePoint Designer 2010 as well as project template in Visual Studio 2010 that can help you to create the model.
If you are interested to explore BCS as an option to integrate PI System with your SharePoint 2010 environment, attached is a tutorial on "Creating a BDC Model to PI using Visual Studio 2010" that guides you to create a BDC model that searches for PI Point and AF Element in your PI System using Visual Studio 2010.