And however odd a request may be, the companies generally do not turn it down. But there are some requests, like helping to find social escorts, which they will decline.
Personal concierges say they often get food delivery requests.
In May this year, A Winsome Life was hired by a woman who works overseas, who asked for a full breakfast to be delivered to her husband for a special occasion.
Mr Melvin Lee, 27, who runs the business with his wife, Ms Jacqueline Teo, also 27, recalls having to buy about $20 worth of pastries and breakfast items from Baker & Cook in Holland Village, which was the husband's favourite cafe.
Mr Lee, who charged about $40 for the service, then delivered the food to a condominium in Yio Chu Kang Road.
He says: "When we rang the doorbell, the husband was very surprised and asked why we woke him up so early on a Sunday. But after we explained that the breakfast was from his wife, he smiled, let us in and thanked us."
Another company, Personal Concierge and Property Management, which has been in the business for about five years, has been cooking and delivering bird's nest soup regularly to a client's parents, who are in their 60s and 70s, for the last five years. It charges a three-figure sum for each delivery.
Personal Concierge's owner, Ms Tan E.T., who is in her 30s, says: "The challenge is in making sure the soup is still piping hot when it reaches their dining table.
"I can't tell you exactly how we keep the soup hot, but it took many tries to 'master' this technique.
"When we first started, I even brought along a slow cooker to the parents' house to re-heat the soup."
Personal concierges also get requests to track down hard-to-find items.
For example, in May this year, a middle-aged woman approached Blitz to help her buy a limited-edition Hermes watch that she saw in a magazine.
The $88,000 watch, crafted in Switzerland, features a red and ochre dial hand-painted by Japanese master artist Buzan Fukushima. Only 12 pieces of the watch exist, but none was sold in Singapore.
Says Blitz's co-founder, Mr Augustine Goh, 28: "We had no luck calling the boutiques here. Thankfully, one of our co-workers used to work in a private bank and had some contacts in the international luxury watch scene.
"We had to extend our reach. After numerous calls, we tracked down one piece in a Hermes boutique in Hong Kong and bought it for the woman immediately. Our service fee was $8,800."
And in March this year, an Australian man in his 20s asked A Winsome Life to buy a pair of special edition Converse sneakers released specially for Chinese New Year.
Says Mr Lee: "He said they were not available in Australia, so we bought a pair in his size at Nex shopping mall for $210 and shipped it to him via FedEx for another $200."
But not all unusual demands come with a hefty fee.
In June this year, Blitz, which started five months ago, received a very odd request - a man asked for condoms to be delivered to a tent in East Coast Park.
Within half an hour, a staff member passed the man a box of condoms at a nearby McDonald's outlet. The delivery fee was $5.
Says Mr Goh: "The request was a little awkward, but we rationalised that the man needed the item and it was our job to provide it."
Some companies, including Concierge Services Singapore and Blitz, have encountered clients who want help in getting social escorts. But that is a line they will not cross.
Says the managing director of Concierge Services Singapore, Ms Jessica Sanchez, who is in her 40s: "It's just something we don't want to be associated with, no matter how much a client offers."
Experts told Life they were not surprised at the unusual demands.
Says Assistant Professor Elison Lim, 40, from the Nanyang Business School: "People are not likely to go to personal concierges for tasks like household chores. Many families in Singapore already have maids who can do that.
"People are more likely to turn to such service providers for tasks which they lack the time, knowledge or skills for, such as planning an unforgettable birthday party or shopping for the perfect gift."
But Associate Professor of Marketing Sharon Ng, 41, who is also from Nanyang Business School, says companies should turn down requests that may involve "illegal, unethical or socially undesirable" behaviour.
"Although you want to be seen as helpful, service-oriented and responsive, it is also important to have ethical standards. In the long run, people are more likely to go to companies they can trust."