The app samples wireless signals to see if data is flowing uninterrupted from routers to phones and tablets.
The app is released alongside research which suggests wi-fi in six million homes and offices is not running as fast as it could do.
The app also provides tips to help people spot what might be slowing down their wi-fi speed.
Interference could come from other electronic devices such as baby monitors, microwaves or Christmas fairy lights, said Ofcom in a statement.
Statistics about home wi-fi speeds are in Ofcom's 2015 Connected Nations report that looks at the state of telecoms and wireless networks in the UK.
The report said there had been "good progress" on the availability and use of telecoms services. About 27% of UK homes now have super-fast broadband that runs at speeds in excess of 30 Megabits per second (Mbps). Last year the figure was 21%.
Super-fast broadband is now available to more than 83% of UK homes - up from 75% in the same period in 2014.
The research also found that those with the higher speed connections to the net are doing more with them. People with faster connections were now making significant use of catch-up TV services, online film rental services and video calls, it said.
Much of the UK's appetite for data was being driven by households that have the super-fast services, said Ofcom.
However, despite the growing use of high-speed broadband it also acknowledged there was "still more to do".
The research found that 2.4 million UK homes, about 8%, cannot get speeds of 10Mbps or more. Many of these homes were in rural areas.
It also said broadband speeds needed to increase for those on the move and said small businesses were being particularly poorly served when it came to access to services of 10Mbps or more. About half of all small or medium-sized firms based in business parks do not have access to net links of such speeds.

The "shocking" incident happened at about 11.55 as the 57-year-old security guard approached the Tesco store in Annick Street in Shettleston.
The robber took the money box before making off in a small white car, later found burnt out nearby.
Police have appealed for anyone with information to contact them.
Officers said the white Hyundai i10 sped away from the scene of the robbery towards Springboig Road. It is believed there was a second man driving the vehicle, although police have yet to provide a description.
Det Insp Clark Hill said: "Due to the fact that it was believed that a firearm was present, our armed response units also attended but have since stood down.
"The suspect knew very well when the van would be there. It certainly wasn't done on the spur of the moment.
"With that in mind, it's possible that the car had been in the area either immediately prior to the robbery or indeed the past few days checking the area out."
No-one was seriously injured in the incident but a security guard, aged 37, from Tesco, who came to the victim's aid suffered a minor injury to his knee after being struck by the car, police said.
He was treated at the scene by paramedics and did not need to go to hospital.
Mr Hill added: "Although thankfully, no-one involved in this incident was seriously injured, this was a terrifying ordeal for the men involved. Also, for it to take place outside a busy supermarket in the middle of the afternoon is just shocking."
Officers have been at the scene carrying out inquiries and are checking CCTV both at the supermarket and in the street.
The suspect is described as being white 5ft 6in tall, of thin build and with a pale complexion. He was wearing a grey hooded top, a "hi-vis" yellow jacket and black jogging bottoms.
Christmas tree lights can slow your wi-fi warns watchdog Ofcom as it releases an app that can check home broadband.
[NEXT_CONCEPT]
An armed robber dressed in a "hi-vis" jacket took at least Â£10,000 from a worker delivering cash to an ATM in the east end of Glasgow.