Was sick of replacing batteries in smoke alarms each year. Bunnings cheapest was 29.95 for a similar product. Please note that these should not be used in QLD as they do not comply with new standards.
Assuming 9v battery is $4 and depending on how many you purchase to spread the cost of shipping, they the devices should pay for themselves in 6 years (not including time saved getting new batteries, swapping them out land the land fill these batteries would most likely go to).
Could be useful to replace 9v battery based alarms in PPOR or IP.
Edit: Just for clarity it's not a bargain if you are purchasing just one BUT if you are purchasing multiple to replace all alarms in your house it will be more cost effective (min 2 to become more cost effective). e.g. 2 * 20.99 + 9.99 = ~$52 vs 2*29.95 = ~$60.
TSK
So by saying equivalent at Bunnings is $29.95 this is actually therefore more expensive and hence not a bargain?