There are currently no mobile screen definitions configured in the site map for the Company Portal. Once Acumatica adds this to the application, a client would be able to login by using the same mobile app.

There’s a suggestion in the Ideas section for this enhancement -- make sure to cast your vote!

P.S. if this is an immediate requirement, please note that the Acumatica framework allows creation and customization of mobile pages, so this could be built by your partner or an external developer. @Cesar Betances of Acumatica made a presentation on this topic recently, see here: 

I can definitely see the value of it. For instance a building owner sees a problem with the HVAC. He/she can take a picture ot eg. the AC unit model number, and submit it with the request (case) for repair. The field technician will be able to see the model, and bring the right parts and tools with him/her when visiting the building owner. No more wasted trips. 

Gabriel, you are the best. We need you.