Device detection via Wireless link

Hello
I am having the following concern. I would like to get from 6 devices (here called transmitters) a signal showing their status ON, these 6 signals should be received by an Arduino Mega (here called Receiver) via a wireless link.
One constraint is that transmitter electronic should be as small and as light as possible.

I am thinking about 2 possible solutions:

  1. Using 6XTLP434 and 1XRLP434 to establish a wireless serial link. Each transmitter will send periodically (e.g. every 2s) a single byte (his identification) that will be read by the receiver. A lack of reception will mean the transmitter is OFF.
    My questions are:
  • Is it possible to establish a point (receiver) multi-point (6 transmitters) link with TLP/RLP434?
  • Or do I need 6 receivers to establish 6 point to point links? In this case what will happen as all transmitters will use the same frequency?
  1. Equipping all 6 devices with a small radio transmitter (e.g. FM) that will emit from 6 different frequencies. Reception of the signals by an FM receiver connected to the Arduino will allow detecting status ON, the lack of signal will mean status OFF. Unfortunately I have no clue how to develop such solution.
    My question is:
  • does someone already did similar implementation or have a link to provide?

I would like to mention that a range of 10m between transmitter and receivers is enough.

Thank you for support and ideas.
Raoul.