Sending logged data with BLE

Question

Hello! I am working on a project in which I want to send stored sensor data to a smartphone whenever the phone is in range or at specific times of day. 
 Most of the communication examples I have found are based on sending data when it is updated by the peripheral, not on sending bulk data. So what is the best way of doing this? I have data from two distinct sensors along with time-stamp data that I want to send and it is important that all the data gets transmitted. 
 So far I have thought that maybe each sensor should have a characteristic and that I should update the values each time it gets read by the phone or something along those lines. The phone would try and read these characteristic values over and over until all the data has been read. Is this a reasonable way to accomplish what I want to do? Examples would be appreciated! 
 I also imagine that the peripheral device (battery driven) should advertise it's presence all the time and that the phone will only scan for it maybe once every hour or so. 
 I have the PCA 10001, nrF 6310 and I have been able to use the examples to transmitt some data to an Android phone. 
 Thanks

Ole Morten · Accepted Answer

What you want is very similar to what the official Glucose Profile/Service does, with its Record Access Control Point. In that setup, a Client writes a command to the Control Point, telling the Server which records it want to receive, and the Server then proceeds to Indicate each of those records on the separate Glucose measurement characteristic. You could easily do something similar for your application, making the Client write the record range he wants to have to a control point, and then making the server Indicate or Notify the data on a separate characteristic. 
 You may also have use in taking a look at nAN-36 and this question . This question (and the one linked in the comment) explains the different roles in play with BLE, while this explains the difference between notifications and indications .