Barcode generator APP

Proactiv specialise in 100% solid plastic cards, keyfobs & loyalty software.

At Proactiv we developed some loyalty software a few years ago. Businesses can subscribe. Once set up they can log in & add clients to the database & allocate a choice of different loyalty schemes amongst other things.
Each customer currently gets a plastic card or keyfob which has a barcode / number which is allocated to each customer. The client can type the name in or scan the card.
What we are looking for is an alternative to the card. We want the customer/client to have the option to use their mobile phone instead of a card/fob.

So an app that produces a barcode (barcode 39)
Open app on phone a barcode pops up on their screen. If it is easy enough for it to bring up their name & the business name. Or possibly the design of a card. Open to ideas.

Our website -proactivmarketing.co.uk is developed in asp.net
The database is MYSQL
We have a dedicated server with a remote desktop connection.
I believe the hosting is in CPanel.