There are different Automation techniques for different industries. How to search for a company that suits your automation requirement ?
Are there any entrepreneurship opportunities in development of custom automation products vertically..?

Petrochemicals
Chemical process industries
Steel & Iron
Thermal power

are some of the core manufacturing companies that use automation products.

 

Just a decade ago it was considered as a saturated market & so called leaders struggled to survive.
See the acquisitions history of Emerson.
Even Google & Microsoft wanted to try that market and never came to public.

Then all of a sudden open source hardware came in like Arduino & Raspberry Pi and they are creeping in industrial automation. Even OpenPLC software can be used in many off the shelf PLCs.

The biggest hurdle here is if something goes wrong, who will own the responsibility and pay for the damages.
Is it the hardware company, or the software company or the integrator ?
Remember chernobil, Union Carbide - Bhopal India or even LG Chem (India) which resulted in multiple thousands of casualties where multi vendor system has created a mess?