bluetooth project with Android. How to scan the piconet, master and slaves

I have a big issue. I would want to create an app on Android (telephone) where should act as a master, and several devices (bluetooth modules) should act as slaves (only piconet, not scatternet). I need that everytime, the master wants to check all avaliable devices near it (for example, an Inquiry process every minute to check an update list of devices around the master), he should obtain this information to know which ones are out of range, powered off or sync.

from lots of questions here on stackoverflow, everybody agrees that making all slaves always discoverable is impossible, because it will drain the battery super fast (so doing the process of Inquiry scan every minute is not feasible). So, which other technical solution could you advice to me?

I have been thinking about something after the master makes de inquiry and paging process, when up to 7 devices are set as active members (Active Member Address), and the rest (up to 256) are put on "parked more" (8 bit Parked Member Address), or Hold or Sniff (this two last ones doesnt get a 'MAC'). A parked device remains synchronized to the master clock and can very quickly become active and begin communicating in the piconet (so other active slave has to be put on parked mode).

Is there any way on Android where i can put switch devices from active to park an viceversa (thro开发者_JS百科ugh AT commands?)? could be useful? Is there any way where i can monitor ALL of them every x seconds?

thank you very much in advance