Two major things apart from regular registrations & approvals for your business would be to:
1. Get an Import Export Code (IEC Code) since your services will be considered as "Export of Services".
2. Secondly you must very careful in dealing with the data and information from the entities as they have strict Data Protection Laws. US data protection laws restricts them from transferring the data from the place of origin i.e you will have to work on their servers without bringing their data to this country.