for me the best are the DPSI from RC-Electronics...(by keeping a original receiver...otherwise the weatronics stuff rocks...)

but sometime place is not enough...so in my F-15 i installed this:

http://www.rc-electronic.com/html/en.../dpsi_bic.html

a great piece of engineering..
he work with NIxx or Lixx battery..
and you get everything: min/max voltage of both battery, peak current, average and direct...regulated output voltage for servo and receivers...and if one battery fail or is not charged he start too beep very loudly...