[{"name":"device1","camera":{"number":3}},{"name":"device2","camera":{"number":1}},{"name":"device3","wifi":{"number":2}}]

db.collection.aggregate([{$match:{$expr:{$gt:[{$reduce:{input:{$objectToArray:"$$ROOT"},initialValue:0,in:{$add:["$$value",{$ifNull:["$$this.v.number",0]}]}}},1]}}}])