Currently use a software I'd like to replicate. Should be easy to recreate format, but backend may take a bit of work I realize. Recreate Payroll program that can be updated with current rates, efile reports and multiple users/companies.
Web based, after the fact or data entry of hours on a periodic basis.
Build database, employee id, various pay items, and payroll tax reports that efile to the IRS. This could be an ongoing project that could produce income past the original creation when rolled out.