The modern TSD rallyist has many low cost tools at their disposal. First there is the GPS. It can serve two functions. The obvious one is it shows a map of where you are and the road configuration. It usually tells you the road you are on and the name of any road you are approaching. Some rally masters even provide pickup points(in case you get lost) as latitude and longitude. So when shopping for a GPS, make sure it has that function. The Garmin Nuvi series is cheap and has all you need. If you have an iPhone 4 you can buy the Garmin GPS app and it has all the functions of the Nuvi.
The Nuvi (and others) also have a trip computer mode. When in this mode you have a remote .10 reading odometer for you navigator to use. The trip meter that comes with your car is usually unreadable from the navigators seat. The trip computer also displays your current speed as well as your average speed witch on rallies with a single speed is very useful for getting surprisingly good scores with no math on your part. Many rally masters now use lots of car zero times and single speed timed sections to take account of the GPS.
Those with an iOS or Android have some other options. I have an iPhone so my emphasis will be on that device. First you need accurate time. There is a free app from Emerald Sequoia called Time that provides accurate time. It gets time from four remote sources and tells you how far your iPhone is off. Usually under 2 seconds but I have seen up to 45 seconds. You need this to either set other clocks or to know the offset needed for other apps that depend on the iPhone for time. If you want the real deal for time purchase a Grundig G8 shortwave radio, about $40 as I recall.
The Richta rally calculator should be your next purchase. It does all the math for you in either seconds or hundredths of a minute. It's $2.99 for the lite version and is available for both iPhone and Android devices. This app does it all. You enter in a speed and an out time and it compares the compute time to the time of day and tells you if you are early or late, You can enter pauses, gains and TAs. It allows you to enter a clock offset (remember the time app) to correct for any time deviation.
To sum it up here is the list of what I recommend. There is a good chance you already own most of the kit.
Garmin Nuvi GPS
Grundig G8 (optional)
Emerald and Sequoia Time app
Recently I purchased the Garmin GPS for my iPhone ($39.99). It is nice because you get the entire North American map downloaded so it works where there are no cell towers or wifi. It also seem to have a more accurate odometer. The Nuvi seems to click over the first .10 mile at about .05 mile. The iPhone app displays this distance in feet until you get to .10 mile.
Another useful app I use is the Dashboard app. It acts as a remote .10 reading odometer based on your GPS position as well as a leg timer. You press reset and it starts the odometer and clock. This is useful for events where you are given a distance and elapsed time for points along the course. These events are sometimes referred to as jogularities.
I hope to see you all soon and I also hope rally masters will take this kit into account when setting up events for the new rallyist.