If the workmen are working in Non-implemented areas of ESI, cover them under WC / Employees' Compensation Policy. Under this policy now there is also a provision for hospitalisation claim due to accident upto Rs. 1 lac with some additional premium.
Additional Term Life Insurance cover is the best option for workmen. This policy provides cover for any kind of death due to accidental or natural and anywhere in India with nominal premium for Group Coverage.
Introduce contributory Group Mediclaim Policy for workmen with reasonable premium deductible from wages and share employer's contribution equivalent to 4.75% for this policy.
If you have large no. of workmen, you can negotiate with insurance companies and reduce the annual premium drastically at least for 1st year and thereafter depending upon claim ratio.