With lipo, you are naked. So the bms, such as it is, is generally you. So you need to do something to be sure you don't overdischarge.
There are HVC- LVC boards you can buy. Then you have a lipo bms. viewtopic.php?f=31&t=36414
And there are various ways to monitor packs. I always recomend new lipo buyers to get a cellog 8. A very handy device for checking packs individual cell voltages quickly. Some buy several, and they become part of the bike.
Others may just monitor the entire packs voltage. This is what I do, combined with not riding farther than the theoretical range of the pack. I use a Cycleanalyst, and running a 10 ah pack, try to be back home on 7-8 ah.
You can use a speedo, or just a set distance you know you can make. Say you work 5 miles from home, and have a pack you know can go 15 miles. Not much to worry about then, riding 10 miles to work and back.
And there are low voltage warning devices. I use them when I am going on long rides, and want to completely discharge one pack, then switch to another.
THE LIPO RULES. NEVER ABOVE 4.3V NEVER BELOW 2.7V DON'T PUNCTURE
Ideal charging /discharging range for Lipo, 3.65v minimum 4.1v maximum
See battery technology section, FAQ thread at the top of the page for lipo noob info.