I donīt know if 50 USD is meant for one person but for one person that gravitates towards outdoor/wilderness/survival this is one of the many possible selections:

Fenix E01 - 15 USD (4sevens.com)
Energizer Lithium 2AAA pack - 8 USD (4sevens.com)
LMF Scout firesteel - 9.95 USD (campingsurvival.com)
WetFire tinder - 8 pieces - 6.08 USD (campingsurvival.com)
ACR Hot Shot signal mirror - 11 USD (REI.com)
ACR whistle - free (comes with hotshot signal mirror) (REI.com)
AMK Heatsheets blanket single - 3.95 USD (REI.com)

total - around 54 USD

alternative:
remove: Energizer Lithium 2AAA pack - 8 USD (4sevens.com)
add: Suunto Micro clipper compass - 8.15 USD (campingsurvival.com)


A knife did not make it to this list because it would be too cheap.

This selection would cover (of course not completely) - daytime and nighttime visual signaling, acoustical signaling, fire making, hypothermia prevention and navigation (alternative).

Of course this selection is sometimes random, there is a lot more comparable gear or different useful gear, itīs just an example what you can buy for 50ą USD. Also the selection of the on-line stores is rather random.
Or like Desperado suggested the AMK PSP - from the description and opinions of people on this forum there seems to be a lot of useful and compact stuff and itīs for very competitive price. And you could add something to it for the remaining money like some nice bottle, ... .

It also depends whether your relatives gravitate more towards long-term emergency prepardness (at home) or outdoor/wilderness /survival.