The Topeak SmartGauge D2 is a must for every toolbox. It is an all purpose pressure gauge and works on bike tires, shocks, motorcycles and cars. Tire pressure is often overlooked, but is critically important for performance riding and floor pumps gauges can vary in accuracy. Low tire pressure can lead to pinch flats and slower time trials. Running too much pressure can lead to unsafe, poor cornering performance especially in criterium racing. Also, lighter riders should use less pressure than heavier riders for safe performance corning. The Topeak gauge will allow you to maintain exact tire pressure to ride your best!
The Meiser listed above in this same section is superior. This gauge is fine, but not great. Its fidgety/difficult/beepy. The feature that lets you slowly come down to the pressure you want is lame compared to Topeaks own Shuttle Gauge. If you just want quick accurate pressure with pretty much no loss in pressure as you check - the Meiser is a better pick from Excel. If you want a gauge to add in front of a pump with no gauge or really want the bleed feature - Topeaks Shuttle Gauge is much more solid and more versatile. Neither of these require batteries. (I have all three and a couple more.) Compared with several other gauges I have, this seems quite accurate. Its just awkward to use due to the pivoting head and it seems to turn on and beep and run out of batteries. 4 stars is generous.