Broken Pack

I have a unique problem I'm looking to solve. I'm a software engineer by trade, but spend most of my free time riding my Harley with a large group of riders. One of the problems we have is sending hand-signals forward to the pack leader. I was thinking about a electronic solution. I'd like to build a small battery powered FM transmitter/receiver. The solution would be mounted onto the handlebar, contain a button/switch and a LED. When we needed to send an alert, one would activate the transmitter - turning on all of the frequency matched LEDs on the other units. Any suggestions?

You are unlikely to get the needed range with a legal, unlicenced, FM transmitter. You might consider the Family Radio Service (FRS) which would give the needed range. There are FRS walkie-talkies which are rather inexpensive and some of them give an audible tone indication when a user transmits ("call button" feature). This can be used to activate an LED fairly easily with an added circuit. Maybe some of them even have an LED indicator.

FRS radios are quiet reasonably priced and that makes things legal.

Digikey has a very amazing and broad selection of RF transceiver devices. They have some wireless communication and related transmitter and receiver units that are rated at around 250 meters outdoors. I did not check all of the specs but there are many different systems available and some probibly have even greater ranges.

The prices range from around $20 on up. I would suspect you could easily build a custom system with what they have.