Investment Instruments Corp., a Newton, Mass.-based company co-founded by Providence resident Owen Johnson...launched the free Rentometer Web service in October.

Visitors to the Rentometer.com Web site can compare their rents to apartments of the same size in their area...The Web site compiles its rental data from active property listings on the Internet, and it provides a comparative market analysis for rental properties in any market with the use of a closely held algorithm, Johnson said.

Investment Instruments created Rentometer in large part to build buzz about its other services, which include iiProperty, a Web-based property management service launched in March that enables landlords to track leases, rental payments and invoices for their properties, Johnston said.

Aside from Johnson, Investment Instruments currently employs two other partners, a team of contractors and some part-time staff.