TOKYO--A Japanese firm on Tuesday unveiled a portable, personal exercise instructor in the form of a headset which will give instant advice by checking the pulse on the wearer's earlobe.

The "Body Trainer" by Sega Toys Co. comprises a phone to be put in the right ear and a tiny clip to be attached to the left ear monitoring the user's heartbeat.

Sega Toys president Isao Kokubun said the product was aimed at establishing a new business field of "medical entertainment."

"We have been pushing for entertainment that adults can also enjoy," Kokubun told reporters. "There is a great potential for products that make you healthy while having fun."

Japan has one of the world's oldest populations, triggering realignment in the toy industry as companies increasingly try to target adult consumers.

The user of Body Trainer chooses one of three modes -- walking, jogging and aerobics -- and accordingly hears rhythmic music and a female voice dispensing advice.

In a 25-minute jogging program, the battery-powered device would say "Let's start warming up" as the user starts trotting.

Taking the person's pulse and considering his or her age, the Body Trainer would offer other pointers, such as "Please exercise a little bit harder."

Sega Toys will launch the product in April in Japan at 5,775 yen (53 dollars) targeting annual sales of 300,000 units. It can also be connected to a music player.

Yoshikazu Itami, an engineering expert who was behind the development of the product, said it was important to pace one's exercise to maximize the health benefits.

"Middle-aged and senior people tend to falsely believe the harder you exercise the more effective the workout is. However, doing it very hard can lead to accidents while doing it too slowly won't be effective," he said.

"People need a system that enables you to communicate with your body," he said.