Business Sense in Mobility of CRM apps

Is there any ROI sense in making CRM mobile?

I can see some ROI stories in Field Service where a field technician can get wireless access to technical documents, make online trouble tickets, get enterprise data relating to equipement, parts etc.
I do not see any ROI stories in Field Sales – If a sales person makes an online lead enquiry, is that going to convert into a sale ( compared to making an online lead enquiry through a wired internet application)

I am not doubting the ROI of CRM but doubting the ROI of mobility of CRM.

Any views on this would be greatly appreciated.

Thanx
isn71