I am using.

http://www.electronickits.com/remote_control/rf2.htm

I bought a second key fob just in case. Never had one go bad but have run the batteries down and it was handy to have the spare standing by.

To do this you must have a solenoid operated windlass. If you are using a wired remote you must already have a solenoid control. I did not drive the solenoid directly from the on board relays. I drive higher rated relays from the on board relays. The outboard relays I use are automotive headlight relays. You can buy sockets for them and they are available at auto parts stores. I think I got mine at All Electronics.

Some arc suppression circuitry is needed on both the input and output of the outboard relays. When a relay is de-energised it actually acts as a small generator and can feedback a voltage pulse strong enough to arc and pit the contacts, shortening relay life. I don't remember the exact circuitry but it involved diodes and capacitors.

Not complicated at all - the relays on the board actuate the additional relays that actuate the solenoid.