If you want Cruise Control there are three options:
MCCruise ... megabucks. Offers a marginally easier instal for those worried about wiring. Works no better than the others
Murphkits (Audiovox, made by Rostra). The most common option. Requires a vacuum reservoir, works well.
Rostra (or Audiovox electronic) Can be a tricky instal, works like a factory set-up.
All of the above require a mechanical connection to the throttle cable assembly. This is not necessarily difficult, but is made considerably easier by googling for help, and removing things that are in the way (like the tank and fuel rail). Can be done with those items in place, but it is tricky and you don't want to be getting it wrong.
I have the ThrottleMeister, as well as the Rostra. It was fitted to the bike when I bought it. I did manage to use it quite effectively during one 3000 mile trip, but it's not easy and at best is a crude device. If cruise control is what you want then all of the throttle locks are simply poor substitutes, and they are not always cheap either.
Yamaha were fitting electronic cruise control to their touring motorcycles in the 1980s. It was a major, and surprising oversight that they failed to do so to the FJR until 2013.