[n0rm]

> range constrained if you are working with power constrained devices

Could you elaborate on that? Why does the narrow frequency drain power?

[freehunter]

Lower frequencies offer longer range, which is nice compared to 2.4Ghz. Which means that 2.4Ghz is also going to have more attenuation, so you need a higher TX power draw to account for that. Basically, to get the same range, 2.4Ghz is going to need more power than 900Mhz would, but 2.4Ghz offers better transmission speed.