Its a risky proposition. Depending on which Airport you are landing in, customs can scan your bag before exiting the airport and any electronics inside will be visible to them.
E.g. in Mumbai, they actually scan ALL check-in bags BEFORE they reach the baggage belt and if its suspicious they mark a big "X" on with with white chalk. Thats a the flag for the customs checkpoint to stop you. They will also ask everyone to scan their hand baggage on a machine before exiting. So unless you open up the package and carry the phone on your person (not in a bag) there is a very high chance of it getting caught.
They aren't so exhaustive in Delhi though. In Delhi they follow more of a "random selection" approach and pick out people whose bags they want to scan based on where they are travelling from (they will ask you that question). I dont know why there is a difference in the process but thats the way it is.
Carrying two phones I wouldnt worry about too much but three is kind of at the point where it gets suspicious. If you end up getting caught or declare them upfront then you'll have to pay 35% customs duty.