The pain Henry Evans felt in his head was so severe, he dropped to his knees and had to crawl to the car that would take him to the doctor.

Evans was suffering a stroke that day five years ago. It robbed him of his ability to walk and speak. But a device developed by a team of high school students now allows Evans, of Los Altos Hills, Calif., to use a laser pointer to do basic tasks with a turn of his head.

The "Laser Finger" was one of several student inventions on display from around the country Wednesday at MIT's annual InvenTeams initiative. Among the other projects: a "fire grenade" that can suppress particularly dangerous blazes and an "A-Pod" that reminds Alzheimer's patients to perform important tasks.

InvenTeams, which is part of the MIT Lemelson program to honor and encourage inventors, is not a competition, but a way to inspire a new generation of inventors, said the program's executive director, Joshua Schuler.

Since the pilot program in 2002, the number of grants -- which range as high as $10,000 -- has grown from three to 20 projects this year.

"We're trying to develop more technically creative young people and give them the confidence they can do this," he said.

Palo Alto High School (Calif.) senior Daniel Shaffer, 17, said The Laser Finger was a project he was happy to spend his spare time on. "It's about Henry," he said.

After Evans' stroke, doctors told his wife, Jane, that he would never recover and advised she place in him a longterm care home. Instead, she took him to Montana for intense therapy, and he eventually regained enough movement in his arm to communicate, sometimes in his fluent German, with computer assistance.

But the stroke also left him unable to do basic tasks if someone wasn't there to attend to him.

"Imagine lying in bed all day," Evans said, speaking through his computer. "I have waited hours to turn on the TV."

Chris Tacklind, the Palo Alto team mentor and a longtime friend of Evans, smiles as he recalls his students' horror thinking of Evans trapped in front of the home shopping channel for hours.

The team developed a laser pointer that can attach to a baseball cap and is activated by a nod of the head. The laser blinks rapidly, creating a light signature that's recognized by a sensor attached to various household devices. When the user turns the laser toward the sensor, it triggers a tiny computer to perform a task, such as turning on a light, or changing the channel.

Tacklind said the Laser Finger could potentially be used to activate anything a remote control can operate, or perform a variety of household tasks, such as turning down the thermostat.

The A-Pod, developed by students at The Bromfield School in Harvard, Mass., in consultation with physicians, is another invention aimed at improving life for people with health problems.

Using wireless communication, the A-Pod reminds Alzheimer's patients to do vital chores such as taking medication, or alerts them if they forget to do something important, such as shut the door.

For example, a sensor on the door sends a signal to the palm sized A-Pod if the door is open too long, setting off an alarm that doesn't stop until the door is shut.

The A-Pod increases an Alzheimer's patient's independence -- which doctors say helps slow the disease -- and also relieves pressure on caretakers, said Bromfield School student Connor MacKenzie.

The idea for the "fire grenade" came to Acton-Boxborough High School student Steve Hart, 16, in a brainstorm he can't explain beyond his awareness of the dangers firefighters face. The grenade is tossed into fires too hot for firefighters to withstand. It releases a gas called FM 200 that absorbs heat and also displaces oxygen, aiming to cool the area enough for firefighters to enter.

The gas is already used in expensive corporate fire suppression systems, but has generally not been available to fight residential fires. The grenade, developed with engineers from Cisco Systems Inc., is just a prototype, and doesn't yet look anything like the teardrop-shaped projectile the team envisions.

"I'll see it through as far as I can," said Hart, who will be a junior next year. "I'm pretty proud of it. I'm proud of what the team has been able to do."